Floating wind turbine platform controlled to optimize power production and reduce loading

ABSTRACT

A method for controlling an inclination of a floating wind turbine platform to optimize power production, or to reduce loads on the turbine, tower, and platform, or both, includes receiving data associated with the inclination of the floating wind turbine platform and wind speed and direction data. An angle of difference between the turbine blade plane and the wind direction is determined, where the angle of difference has a vertical component. A platform ballast system is then caused to distribute ballast to reduce the vertical component to a target angle chosen to optimize power production, or reduce turbine, tower, and platform loads, or both.

CROSS REFERENCE

This application is a continuation of U.S. patent application Ser. No.16/427,208, entitled “Floating Wind Turbine Platform Controlled ToOptimize Power Production And Reduce Loading,” filed on May 30, 2019,the content of which is hereby incorporated by reference.

This application is related to U.S. patent application Ser. No.14/841,673, entitled “Floating Wind Turbine Platform With BallastControl And Water Entrapment Plate Systems,” filed on Aug. 31, 2015, nowU.S. Pat. No. 9,446,822, which is a continuation of U.S. patentapplication Ser. No. 14/218,805, entitled “Asymmetric Mooring System forSupport of Offshore Wind Turbines,” filed on Mar. 18, 2014, now U.S.Pat. No. 9,139,266, which is a continuation of U.S. patent applicationSer. No. 13/925,442, filed Jun. 24, 2013, now issued as U.S. Pat. No.8,692,401, on Apr. 8, 2014, which is a continuation of U.S. patentapplication Ser. No. 12/988,121, filed Oct. 15, 2010, now issued as U.S.Pat. No. 8,471,396, on Jun. 25, 2013, which is a national stageapplication of PCT Patent Application No. PCT/US2009/039692, filed Apr.6, 2009, which claims priority to U.S. Provisional Patent ApplicationNo. 61/125,241, titled “Column-Stabilized Offshore Platform WithWater-Entrapment Plates And Asymmetric Mooring System For Support OfOffshore Wind Turbines” filed Apr. 23, 2008, the contents of each ofwhich are hereby incorporated by reference.

This application is also related to U.S. patent application Ser. No.15/856,655, entitled “Methods For Controlling Floating Wind TurbinePlatforms,” filed on Dec. 28, 2017, which is a continuation of U.S.patent application Ser. No. 14/283,051, entitled “System and Method forControlling Offshore Floating Wind Turbine Platforms,” filed on Mar. 20,2014, now U.S. Pat. No. 9,879,654, which claims priority to U.S.Provisional Patent Application 61/825,412, entitled, “Fully-IntegratedControl System for Offshore Floating Wind Turbine Platforms,” filed onMay 20, 2013, the contents of each of which are hereby incorporated byreference.

This application is also related to U.S. patent application Ser. No.14/924,448, entitled “Connection System for Array Cables ofDisconnectable Offshore Energy Devices,” filed on Oct. 27, 2015, whichclaims priority to U.S. Provisional Patent Application 62/069,235,entitled, “Connection System for Array Cables of Disconnectable OffshoreEnergy Devices,” filed on Oct. 27, 2014, the contents of each of whichare hereby incorporated by reference.

This application is also related to U.S. patent application Ser. No.15/799,964, entitled “Semi-Submersible Floating Wind Turbine PlatformStructure With Water Entrapment Plates,” filed on Oct. 31, 2017, whichis a continuation of U.S. patent application Ser. No. 15/186,307,entitled, “Floating Wind Turbine Platform Structure With OptimizedTransfer Of Wave And Wind Loads,” filed on Jun. 17, 2016, now U.S. Pat.No. 9,810,204, the contents of each of which are hereby incorporated byreference.

FIELD

The invention relates to floating wind turbines, and in particular, tocontrollers for adjusting the inclination of floating wind turbines.

BACKGROUND

Offshore wind energy is a very promising source of renewable energy forthe reason that offshore wind is more intense and uniform than on-landwind. To harness wind energy in deeper water further offshore, onesolution is to build floating wind turbines. Floating wind turbines facetechnical challenges that are different from both on-land wind turbinesand floating oil and gas platforms.

In contrast to onshore wind turbines, a floating wind turbine requires aplatform that provides buoyancy to support the weight of the wholestructure. The structure of the platform may have severalcylinder-shaped columns with large diameters. Besides providingbuoyancy, the platform combined with the wind turbine generator shouldbe able to resist dynamic wind, wave, and current loads, and provide astable support for power production. Another challenge is the addedfatigue damage from wave load, which might be comparable to that fromwind load. These loads require the platform to have a robust structuraldesign to achieve better reliability. The traditional way to strengthenthe structure is to reinforce with large number of welded stiffeners,which may not be cost efficient and which add weight that is undesirablefor a floating platform.

An additional challenge associated with floating wind turbines is theneed to minimize their motion dynamics to optimize turbine performanceand minimize platform steel weight. Offshore floating wind turbines aretypically designed with a specified motion envelope around theireven-keel equilibrium position. The equilibrium position is typicallychosen to be zero degrees for combined roll and pitch motions to keepthe tower vertical as often as possible, which replicates the operatingconditions of a land-based or bottom-fixed wind turbine.

Also, for typical existing wind turbines, the power production is cappedto the power at rated wind speed. After the rated wind speed is reached,the blades are pitched to stay at this maximum power production—tryingto produce more power would require a change of hardware in the turbineitself.

FIG. 1A and FIG. 1B illustrate prior art wind turbine rotor nacelleconfigurations. Existing horizontal axis wind turbines (HAWTs) 100, 150present two main components: a tower 102, 152 and a rotor nacelleassembly (RNA) 104, 154. RNA 104, 154 include rotor blades 106, 156 andhubs 110, 160. RNA 104, 154 also include the rotor shaft located insidethe nacelle with a rotor shaft axis 108, 158. Blades 106, 156 aresupported by hubs 110, 160, located at the end of the rotor shaft. Theterm “horizontal” is a misnomer used to differentiate from turbines inwhich the rotor shaft is vertical. As explained, a rotor plane 112, 162is slightly tilted from the tower by a fixed offset angle 114, 164(measured with respect to the tower), which, when the tower is vertical,results axes 108, 154 not being horizontal and blade planes 112, 162being a global offset angle ε from the vertical. Global offset angle ε,however, will change if the tower is inclined.

Because the wind speed and direction can change frequently a windturbine controller utilized on a floating platform is typically providedwith a wind direction system including a wind direction sensor and a yawcontrol system. Yaw is defined as rotation of the nacelle about the axisof tower 102, 152, i.e., rotation about an axis that is perpendicular tothe horizontal plane. The yaw control system may be housed withinnacelle 104, 154. When the wind direction sensor detects shifts in thewind direction, the yaw control system will rotate the nacelle (yaw) atthe top of the tower to point the nacelle in the direction of the wind.If an angular offset is detected by the wind direction sensor, thecontroller can actuate a yaw motor that rotates nacelle 154, hub 160,and turbine blades 156 about tower 102, 152.

In addition, the wind turbine controller is typically provided with awind speed sensor that is coupled to a turbine pitch control system. Inresponse to changes in detected wind speed the turbine pitch controlsystem responds by inducing a change in the pitch of the turbine bladesto optimize the output power or minimize the wind drag forces on theturbine blades.

The three blades of a typical HAWT, however, present a peculiarity: therotor shaft is not horizontal—it is tilted an offset angle 114, 164 withrespect to the horizontal. This inclination moves the weight and thrustof rotors 106, 156 more directly over towers 102, 152. It also increasesthe clearance between blades 106, 156 and towers 102, 152, whichdecreases aerodynamic disturbance between the tower and the blades. Foran upwind turbine 100, the increased clearance also reduces theprobability of blade 106 striking tower 102 (from wind force bending theflexible blade). For a downwind turbine 150 (where the air encountersthe tower first and then the blades) the risk of blades 156 bending andstriking tower 152 is smaller than for upwind turbine 100. Still, fordownwind turbine 150, tilting nacelle 154 upward reduces the wake effectfrom the tower on the passing blades. The wake effect results in achange to the lift of the blade as it passes the tower and this changecreates a corresponding cyclic change to the moment caused by the bladeat the hub. Therefore, blade planes 112, 162 are usually tilted atpositive fixed offset angles 114, 164 (usually between approximatelyfour and eight degrees) for both upwind and downwind configurationswhere positive offset angles 114, 164 are measured between blade planes112, 162 and towers 102, 152.

Due to global offset angle ε, the projected rotor area is slightlydecreased compared to what it would be if the shaft were horizontal andthe rotor plane vertical (see Equation 2, within). For wind speeds lessthan rated wind speeds (or “sub-rated” or “under-rated” wind speeds),when the rotor speed is ramping up with the wind speed, the decreasedprojected area results in an energy loss. In addition, a tilted rotorcan cause unnecessary loadings on the rotor drive train and tower.

Thus, there is a need for offshore wind turbines to have a structuralplatform design that provides load bearing capacity, hydrodynamicstability, and good reliability with minimized cost, and which improvesthe power produced when winds are at less than rated speeds.

BRIEF DESCRIPTION OF THE FIGURES

The embodiments are illustrated by way of example and not limitation inthe figures of the accompanying drawings, in which like referencesindicate similar elements, and in which:

FIG. 1A and FIG. 1B illustrate prior art wind turbine rotor nacelleconfigurations;

FIG. 2A and FIG. 2B illustrate a floating platform at even keel vs. afloating platform heeled into the wind according to an embodiment;

FIG. 3 is a top plan view illustrating a floating platform according toan embodiment;

FIG. 4 is a perspective view illustrating local and global roll andpitch reference frames on a floating platform according to anembodiment;

FIGS. 5A, 5B, and 5C illustrate relative angles between the tops ofcolumns of a floating platform and the horizontal according to anembodiment;

FIG. 6 is a chart illustrating power curves for a generic 8 MW windturbine operating at even keel and a generic 8 MW wind turbine operatingwith six degrees of heel into the wind according to an embodiment;

FIG. 7 is a chart illustrating the power produced with a random seastate and less-than rated wind speed (8 m/s) for a generic 8 MW windturbine operating at even keel and a generic 8 MW wind turbine operatingwith six degrees of heel into the wind according to an embodiment;

FIG. 8A is a chart illustrating the thrust force at the nacelle vs. windspeed with a random sea state for a generic 8 MW wind turbine operatingat even keel and a generic 8 MW wind turbine operating with six degreesof heel into the wind according to an embodiment;

FIG. 8B is a chart illustrating the bending moment at the tower base vs.wind speed with a random sea state for a generic 8 MW wind turbineoperating at even keel and a generic 8 MW wind turbine operating withsix degrees of heel into the wind according to an embodiment;

FIG. 8C is a chart illustrating the yaw bearing force vs. wind speedwith a random sea state for a generic 8 MW wind turbine operating ateven keel and a generic 8 MW wind turbine operating with six degrees ofheel into the wind according to an embodiment;

FIG. 9 is a chart illustrating an example of a determination of optimumheel angle for a generic 8 MW floating wind turbine with a random seastate and less-than-rated wind speeds over a twenty-five-year periodaccording to an embodiment;

FIG. 10 is a chart illustrating capacity factors for a generic 8 MWfixed bottom wind turbine, a generic 8 MW floating wind turbine at evenkeel, and a generic 8 MW floating wind turbine at an optimum heel angleinto the wind according to an embodiment;

FIG. 11A is a flowchart of an embodiment of a method;

FIG. 11B is a flowchart of an embodiment of a method;

FIG. 12 shows a floating wind turbine platform with decoupled marinesystem and wind turbine controllers according to an embodiment;

FIG. 13 shows a floating wind turbine platform with an integratedfloating wind turbine controller according to an embodiment;

FIG. 14 is a flow chart for the control of a floating platform accordingto an embodiment;

FIG. 15 is a flowchart for an integrated controller according to anembodiment;

FIG. 16 is a flowchart for an integrated controller according to anembodiment;

FIG. 17 conceptually illustrates an example electronic system with whichsome embodiments of the subject technology may be implemented; and

FIG. 18 illustrates an exemplary arrangement of floating wind turbineplatform in a wind farm.

DETAILED DESCRIPTION

The subject matter discussed in the background section should not beassumed to be prior art merely as a result of its mention in thebackground section. Similarly, a problem mentioned in the backgroundsection or associated with the subject matter of the background sectionshould not be assumed to have been previously recognized in the priorart. The subject matter in the background section merely representsdifferent approaches, which in and of themselves may also correspond toembodiments of the claimed inventions.

The following detailed description is made with reference to thetechnology disclosed. Embodiments are described to illustrate thetechnology disclosed, not to limit its scope, which is defined by theclaims. Furthermore, aspects of one embodiment may be combined withaspects of another embodiment to create an additional embodiment. Thoseof ordinary skill in the art will recognize a variety of equivalentvariations on the description.

The subject matter in this disclosure provides apparatuses and methodsallowing regular HAWTs to be operated with efficiencies on a floatingfoundation that are increased over the operation of the same HAWT on afixed foundation that cannot heel. With a typical wind turbine on atypical platform at the equilibrium position of zero degrees, when therotor speed is ramping up or at speed, the decreased projected area dueto the non-vertical blade swept plane (i.e., rotor plane) results in anenergy loss. In an embodiment, the energy loss is avoided by incliningthe rotor into the wind to bring the rotor plane to or sufficientlyclose to perpendicular to the horizontal axis, i.e., bring a to zero orsufficiently close thereto. In such embodiments, the ballast (e.g.,water) present in the floating platform hull is moved using a marinesystem controller (or a “platform controller”) to incline the floatingplatform at a target angle that maximizes the rotor projected area and,thus, maximizes the power produced at a given wind speed. In suchembodiments, instead of the standard tower vertical equilibrium settingof zero-degrees inclination (i.e., a vertical tower), the inclination ofthe tower is targeted to reduce or eliminate the global angle ε that therotor plane is inclined from vertical—typically 6 degrees when the toweris vertical. Thus, in an embodiment, the optimum angle at which theplatform is inclined into or away from the wind is dependent on the meanwind speed and wind direction, and is chosen to make the turbine rotorplane perpendicular to the wind direction. Since the angle of theturbine rotor plane to the wind direction can be measured as a sum of ahorizontal component (related to the wind direction) and a verticalcomponent (related to the inclination of the rotor plane into or awayfrom the wind), in the embodiment, the target for the vertical componentis zero degrees. As discussed within, the target for the verticalcomponent, or “vertical target angle,” may be attained by inclining theplatform an optimum heel angle (δ_(optimum)).

In an embodiment, the floating platform is inclined to the target angleonly for wind speeds that are below the rated speed of the wind turbine.In an embodiment, the floating platform is inclined to the target angleonly for wind speeds that are above a minimum wind speed and also belowthe rated speed of the wind turbine. For example, the wind turbine mayrequire a minimum wind speed of 4 m/s to produce electricity, and may bedesigned to produce a maximum amount of electricity with wind at a ratedspeed of 11 m/s.

In an embodiment, when the tower is inclined into the wind, the weightof the RNA and tower create a righting moment about the base of thetower that counteracts the heeling moment created by the aerodynamicrotor/wind interaction. The extend of the righting moment is determinedby the weight of the RNA and tower and the distance the center ofgravity of the RNA and tower is advanced toward the wind from the baseof the tower, which is a function of the platform inclination angle.This righting moment results in a reduction in the moment that must beresisted throughout the tower and particularly at the base of the towerby the floating platform structure. The embodiment thus lowers staticloading on the turbine, the tower base, and the floating structurewithout reducing the power at a given wind speed. In an embodiment, thefloating platform may be inclined to the target angle only for windspeeds that are above a minimum wind speed.

In an embodiment, bringing the shaft closer to horizontal or tohorizontal also reduces the gravity component of force along thedirection of the shaft, reducing the axial loading of the nacellebearings and associated structure. In the embodiment, with a typicalwind turbine on a typical level platform, the non-vertical rotor causesan unnecessary load on the RNA drive train in the direction of the rotorshaft. For example, in the upwind turbine of FIG. 1B, the non-horizontalangle of shaft 158 results in the weight of the rotors 156 and hub 160imparting a gravity component of force in the direction of shaft 158.This force along shaft 158 must be countered by opposing forces in thebearings and other structure of RNA 154, adding to the thrust forcethose components encounter caused by the rotor/wind interaction. In theembodiment, the axial loads are reduced by introducing a targetinclination to the floating platform that brings the rotor plane closerto the vertical axis.

In an embodiment, depending on: the wind speed; the wind profile; thesea state; or the turbine status, the target angle of platforminclination may also be set to a value slightly different from theinitial value of a to maximize rotor power efficiency. That is, in thisembodiment the desired final value of ε may not be zero. In other words,this disclosure describes different processes and methods that may beused to find an optimum platform angle δ_(optimum) for differentenvironmental and turbine parameters, where δ_(optimum) may be differentfrom the initial value of ε (and different from fixed offset angles 114,164, 214 (FIG. 2A), 264 (FIG. 2B). In response to finding an optimumangle δ_(optimum), the active ballast controller is adjusted to targetthe optimal heel angle δ_(optimum). In an embodiment, δ_(optimum) may bedetermined by measuring power output at varying heel angles andchoosing, as the target heel angle, δ_(optimum), the heel angle thatproduced the maximum power. In an embodiment, δ_(optimum) may be dynamicand maintained by a closed loop feedback system with inputs of poweroutput and heel angle. In an embodiment, data of the power output of theturbine may be obtained by an active ballast controller or an integratedcontroller from sensors or other measuring equipment at a powerconnection on the platform, a power line from the turbine, or asubstation on the platform or elsewhere.

Thus, in general, the various embodiments take advantage of the abilityof a floating platform to change its inclination to incline the rotor toincrease power production and decrease loads on the RNA and loads at thebase of the tower. And, in the various embodiments, the methods used toadjust the ballast to the targeted heel angle may be those disclosed inU.S. patent application Ser. Nos. 12/988,121 and 14/283,051, which areincorporated by reference in its entirety.

FIG. 2A illustrates a floating wind turbine and platform 200 at evenkeel versus, in FIG. 2B, an identical floating wind turbine 250 heeledinto the wind according to an embodiment. Wind turbines and platforms200, 250 both have upwind turbines with towers 202, 252, RNAs 204, 254.RNAs 204, 254 include rotor blades 206, 256 and turbine shaft axes 208,258 creating rotor planes 212, 262. Rotor planes 212, 262 are slightlytilted from the tower by a fixed offset angle 214, 264. Rotor planes212, 262 are a global offset angle ε 215, 265 from the vertical (globaloffset angle 265 is zero degrees). Floating platforms 216, 266 includescolumns 218, 220 and 268, 270 with ballast 226, 228 and 276, 278,respectively. In FIG. 2A and FIG. 3B, a third column 222, 272 is behindcolumns 220, 270, respectively. Column 222 is illustrated in FIG. 3 .Column 272 is illustrated in FIG. 5B and FIG. 5C. In some embodiments,δ_(optimum) may be chosen to completely eliminate offset angle ε 215,bringing it to zero as shown in angle offset angle ε 265. In otherembodiments, δ_(optimum) may be chosen such that offset angle ε 215 isnot completely eliminated and inclining platform 266 to the targetedδ_(optimum) results in an offset angle ε that is non-zero.

For a wind turbine, e.g., floating wind turbines and platforms 200, 250,power varies according to.P=½ρA _(apparent)(ε)C _(p)(ε)V ³  Equation 1

Where:

-   -   ρ is the density of air,    -   A_(apparent) is the rotor swept area,    -   C_(p) is the power coefficient,    -   V is the wind speed, and    -   ε is the global rotor plane tilt angle with respect to the        vertical (e.g., global offset angles 215, 265), or the global        rotor shaft tilt angle with respect to the horizontal.

In Equation 1, the rotor area encountered by the wind is not the rotorabsolute area A, but the projection of this area on the vertical axisA_(apparent):A _(apparent) =A cos ε  Equation 2

Increasing the rotor swept area by tilting the platform to compensatefor ε therefore increases the power production of the turbine. In anembodiment, compensating for ε translates into physically leaning theplatform backwards (for a downwind turbine) or forwards (for an upwindturbine) by this angle. In an embodiment illustrated in FIG. 2A and FIG.2B, the lean is accomplished by shifting platform ballast 226, 228,which is split between columns 218, 220 to cause column 270 to floatlower in the water than column 268. Thus, global rotor plane offset ε215 is reduced from fixed offset angle 214 to global rotor plane offsetε 265, which is zero degrees.

By increasing the apparent rotor plane area for less-than-rated windspeeds (wind speeds for which the turbine is not producing its maximumpower), embodiments increase the power production of the floating windturbine while the rotor speed ramps up to its rated speed.

In addition, for all wind speeds, inclining the rotor to compensate forε would cause the rotor plane to be perpendicular to the incoming windflow. As discussed, when the rotor plane is not vertical, i.e., whenthere is a non-zero vertical component of the rotor angle ofinclination, gravity works on the rotors and hub to create an addedcomponent of force parallel to the rotor shaft axis—an addition to thethrust force caused by the wind (See FIGS. 8A, 8B, and 8C and relatedtext)—in an amount proportional to the sine of ε multiplied by the massof the RNA and gravity. This rotor and hub gravity component loadcreates a moment that is transferred to the base of tower andcontributes to the bending moment loads at the bottom of tower and onthe floating structure. Therefore, reducing the horizontal force at thetop of tower leads to a direct reduction of the loads at the base oftower and on the floating platform. Furthermore, inclining the tower andRNA into the wind creates a righting moment that counteracts the heelingcaused by the aerodynamic forces from rotor/wind interaction.

FIG. 3 is a top plan view illustrating floating platform 216 accordingto an embodiment. In FIG. 3 , an angle

302 denotes the interior angle between columns 218, 220, 222 of floatingplatform 216. As said, floating platform 266 is identical.

FIG. 4 is a perspective view illustrating local and global roll andpitch reference frames on floating wind turbine and platform 200according to an embodiment. In FIG. 4 , details of the global windreference frame (global roll α 402 and global pitch β 404) and platformlocal wind reference frame (local roll α 406 and local pitch β 408) aredescribed with respect to the floating wind platform and turbine 200.For an oncoming wind, φ represents the angle between the wind direction410 and the platform primary axis. Local roll α 406 is measured aboutthe platform primary axis. An optimum global heel angle (δ_(optimum))may be defined as the combination of an optimum global roll angle(α_(global,optimum)) and an optimum global pitch angle(β_(global,optimum)) according to the following, which is applicable forsmall angles.δ_(optimum)=√{square root over((α_(global,optimum))²+(β_(global,optimum))²)}  Equation 3The targeted local platform roll angle (α_(set)) and targeted localplatform pitch angle (β_(set)) may be defined as:β_(set)=cos(φ)β_(global,optimum)+sin(φ)α_(global,optimum)  Equation 4α_(set)=−sin(φ)β_(global,optimum)+cos(φ)α_(global,optimum)  Equation 5As a result, the targeted relative angles between column 218, 220, 222top centers can be computed by the following equations (see FIG. 5A,FIG. 5B, and FIG. 5C, and further related discussion within):θ_(1-2,set)=−(sin(γ)β_(set)+cos(γ)α_(set))θ_(1-3,set)=−(sin(γ)β_(set)−cos(γ)α_(set))θ_(2-3,set)=α_(set)  Equations 6A, 6B, 6CFor a given pair of columns i, j, the difference between the targetangle (θ_(i-j,set)) and the measured angle (θ_(i-j)) is an error(e_(i-j)) that may be used as an input to the controller:e _(i-j)=θ_(i-j,set)−θ_(i-j)  Equation 7

In Equation 7, the following convention is used. If the error (e_(i-j))is negative, i.e., θ_(i-j) is larger than θ_(i-j,set), it means thatcolumn i is higher relative to column j than the target value. Based onthe error e_(i-j) being negative, the correct process is to move ballastfrom column j to column i. In an embodiment, this process will proceedprovided that the absolute value of the error (|e_(i-j)|) is greaterthan a pre-determined value that defines a first (or “ON”) dead-bandaround the targeted heel angle. In the embodiment, the process will notproceed, or will stop, when the absolute value of the error (|e_(i-j)|)is less than a pre-determined value that defines a second (or “OFF”)dead-band around the targeted heel angle. Depending on the relativeangles θ_(i-j) between the several columns, ballast may be moved fromone or more of the several columns in the same time. By considering therelative angles between all the column top centers in this manner, thefastest water transfer path to achieve the target angles are alwaysconsidered. Thus, the active ballast system is controlled to drive theplatform to reach the optimum heel angle as quickly as possibleregardless of the relative errors between the columns.

In an embodiment, if one of the pumping systems is suddenly deficient, aredundant pumping system is employed according to the approach ofEquations 3 through 7.

In an embodiment, a standard Proportional-Integral-Derivative (PID)controller may be used in the correction of the heel angle error.

In an embodiment, a more complex control logic may be used (e.g., aKalman filter, or others) in the correction of the heel angle.

FIG. 4 illustrates that the plane of rotor blades 206 may benon-perpendicular to wind direction 410 should turbine shaft axis 208 beout of alignment with wind direction 410 by being rotated about tower202—such misalignment would add a horizontal angular component of error.In addition, platform 216 may be improperly tilted about the axis ofglobal pitch β 404—such misalignment would add a vertical component oferror.

In an embodiment where the optimum global roll angle(α_(global,optimum)) is zero degrees, which is the preferable condition,Equation 3 reduces to:δ_(optimum)=β_(global,optimum)  Equation 8As a result, the targeted local platform roll angle (α_(set)) andtargeted local platform pitch angle (β_(set)) may be defined as:β_(set)=cos(φ)β_(global,optimum)  Equation 9α_(set)=−sin(φ)β_(global,optimum)  Equation 10Equations 6A, 6B, 6C for the targeted relative angles between column topcenters are unchanged.

FIG. 5A, FIG. 5B, and FIG. 5C illustrate relative angles between thetops of columns 268, 270, 272 of floating wind turbine and platform 250and the horizontal according to an embodiment. In an example, for atriangularly-shaped platform with three columns, based on the filteredplatform roll angle α and filtered platform pitch angle β, the relativeangles θ_(i-j) between column top centers i and j (where i and j denoteone of the three columns 268, 270, 272), may be determined usingEquations 6A, 6B, 6C. Again, angle

302 denotes the interior angle between columns 218, 220, 222 as shown inFIG. 3 . Equations 6A, 6B, and 6C are adapted for platforms with columnsat the vertices of an isosceles or equilateral triangle. These equationsmay be modified to account for other triangular arrangements or they maybe modified to account for platforms of other shapes. As FIG. 5Billustrates, rotor plane 262 may be vertical even where platform 266 istilted to the side. While this is not an optimum situation for theplatform, it would not negatively impact power generation.

FIG. 6 is a chart illustrating power curves (power produced vs. windspeed) for a generic 8 MW wind turbine operating at even keel (dottedline) and a generic 8 MW wind turbine operating with six degrees of heelinto the wind (solid line) according to an embodiment. FIG. 6 shows thatoptimizing the rotor plane angle enables the turbine to produce morepower at smaller wind speeds and therefore increases the efficiency ofthe HAWT in converting the energy in the available wind into electricalpower.

FIG. 7 is a chart illustrating the power produced with a random seastate and less-than rated wind speed (8 m/s) for a generic 8 MW windturbine operating at even keel and a generic 8 MW wind turbine operatingwith six degrees of heel into the wind according to an embodiment. FIG.7 focuses on one wind speed, showing, over time, the potential gain ofpower obtained by heeling the platform to compensate for ε. In FIG. 7 ,the power produced at a six-degree angle of inclination (solid line) isconsistently higher than when the turbine is operating at even keel(dotted line). Similar predictions should be valid for all HAWTs with anangled rotor.

FIG. 8A illustrates the effect of platform inclination on the nacellethrust force, e.g., the force experienced by RNA 204, 254 in thedirection of axes 208, 258 (FIG. 2A, FIG. 2B). FIG. 8B illustrates theeffect of platform inclination on the bending moment experienced at thebase the tower, e.g., the bending moment where tower 202, 252 isattached to platform 216, 266 (FIG. 2A, FIG. 2B). FIG. 8C illustratesthe effect of platform inclination on the internal yaw bearing forcemeasured perpendicularly to the tower longitudinal axis. In FIG. 8A,FIG. 8B, and FIG. 8C, the effect of platform inclination is illustratedby comparing a generic 8 MW upwind turbine with a 6 degree inclinationoperating on a floating platform at even keel to the same wind turbineoperating on a floating platform inclined 6 degrees into the wind (suchthat the angle between the rotor plane and vertical is close to zero)for wind speeds varying from 0 m/s to 35 m/s. FIG. 8A shows asignificant decrease in the loads at the nacelle when the turbine isheeling towards the wind and the rotor plane is close to the vertical(i.e., a decrease of approximately 20,000 N of thrust force). FIG. 8Bshows a significant decrease in the load at the tower base when theturbine is heeling towards the wind and the rotor plane is close to thevertical (i.e., a decrease of approximately 50,000 N of bending moment).And FIG. 8C shows a significant decrease in the yaw bearing load whenthe turbine is heeling towards the wind and the rotor plane is close tothe vertical (i.e., a decrease of approximately 25,000 N of yaw bearingforce). This illustrates the multiple benefits of inclining the floatingplatform: a reduction in loads at both the nacelle and at the base oftower and supporting platform, and an increase in power generation.

In embodiments discussed above, the optimum platform heel angle(δ_(optimum)) is chosen to match closely the fixed rotor plane tiltvalue such that ε is reduced to zero. In other embodiments, however, theoptimum platform heel angle (δ_(optimum)) may be different from theinitial value of ε such that ε is not completely eliminated. In suchembodiments, the optimum platform heel angle (δ_(optimum)) may be chosento result in a non-zero ε to account for, for example, varioussea-states, wind characteristics, or turbine status. In suchembodiments, there may be a number of processes for determining theoptimum rotor plane angle: 1) the angle may be determined in advance fora range of conditions using numerical simulations, 2) determined inadvance for a range of conditions using machine learning, 3) determinedin real-time and directly on the floating wind turbine platform using,e.g., a power-generation feedback loop, and 4) determined first at asecond wind turbine platform and subsequently communicated to the firstfloating wind turbine platform.

In embodiments determining δ_(optimum) using numerical simulations, thefollowing non-exhaustive list of site characteristics may be considered:environmental characteristics such as wind, wave, current, water depth,or soil data; turbine and platform status such as whether the turbine isproducing power, parked, with a fault (from the turbine or activeballast system controller), starting up, or shutting down; platformmotions; turbine motions; platform loads; and turbine loads. Such datamay be used to develop computational models. Various combinations of thedata may be input into the models to find optimum heel angles for thevarious combinations of data.

In an embodiment, a plurality of floating wind turbines platforms can bearranged in an array. With reference to FIG. 18 , an exemplaryarrangement (i.e., a “wind farm”) of floating wind turbines platforms200 is illustrated. Since the wind velocity is reduced and madeturbulent when it flows through a wind turbine, in one embodiment, thewind turbines are separated by a radius 355 of about 10 wind turbinerotor diameters or more and arranged in multiple staggered lines 329,331, 333 that are perpendicular to the most frequent wind direction 335.In the illustrated embodiment, the floating wind turbine platforms, e.g.platform 200A, are equally separated from six adjacent wind turbines200B . . . 200G, by 10 turbine diameters. Because of the staggeredconfiguration, the wind blowing between two floating wind turbinesplatform 200B, 200G in the first row 329 will have a clear path to thefloating wind turbines platforms 200A, 200C, 200F in the second row 331.This wind path will be clear even if the wind direction has shifted upto 30 degrees away from the preferred direction. The floating windturbines platform 200D, 200E in the third row 333 may be in line withthe floating wind turbine platforms 200 in the first row 329, however,since there is a separation of about 17 turbine rotor diameters, theloss of power due to up wind turbulence is negligible. Even if the winddirection shifts to an angle that aligns the adjacent floating windturbine platforms 200, a 10 turbine rotor diameter separation will onlyhave a minimal effect on power output.In an embodiment, numerical simulations using such data may also becreated for a complete floating wind farm with the simulations providinga δ_(optimum) for each platform of the wind farm for a given set ofconditions. In the embodiment, the δ_(optimum) may or may not be thesame for any two platforms. The embodiments may be used to optimizepower production for the wind farm as a whole, which might result in oneof more of the platforms in the wind farm producing at less-than-optimumpower. Similarly, an embodiment may be used to optimize loading for thewind farm as a whole, which might result in one or more of the platformsin the wind farm experiencing less-than-optimal loading. And, in anembodiment, a wind farm simulation may also provide a prediction foreach individual platform of a time at which the platform should expectto begin experiencing the predicted conditions. In an embodiment,information from the simulation may be provided to a controller for anindividual platform, which may use that information to time the transferof ballast so that the platform achieving the optimal inclination (foroptimal power or optimal loading or both) coincides with the arrival ofthe predicted conditions. In an embodiment for determining theδ_(optimum) for optimizing power or loads or both, a platform controlleron a floating wind turbine platform within a wind farm may receive windspeed and direction data. The platform controller, using the wind speedand direction data, may determine a simulation for the windfarm thatcorresponds to the wind speed and direction data. The platformcontroller may direct a ballast control system on the platform toachieve the δ_(optimum) from the corresponding simulation. The platformcontroller also may provide, to the controllers of the other floatingwind turbine platforms of the windfarm, information regarding thecorresponding simulation (e.g., the actual simulation or informationallowing the other controllers to determine the correspondingsimulation). The other controllers then may direct their respectiveballast control systems to achieve their respective δ_(optimum) from thecorresponding simulation. In an embodiment, the corresponding simulationmay include a time for each platform controller to begin directing theirrespective ballast control system to achieve their respective theδ_(optimum). In an embodiment, the corresponding simulation may alsoinclude, for each platform, a delay that each platform controller is towait before directing their respective ballast control system to achievetheir respective the δ_(optimum). In an embodiment, the first platformmay controller may determine from the data and the platform's locationwithin the wind farm that the floating wind turbine platform is thefirst floating wind turbine platform of the wind farm to experience theweather conditions represented by the wind speed and direction data. Thefirst platform controller may include, with the information regardingthe corresponding simulation, the time of arrival of the wind conditionssuch that the delay of each controller is to be measured from the timeof arrival. In an embodiment, the corresponding simulation may be chosenfrom a database of simulations, or may be computed by each platformcontroller based on the received data.

In an embodiment, a wind farm will have floating wind turbine platformsat the periphery of the wind farm. Depending on the direction ofoncoming weather conditions, one or more of the peripheral platformswill experience the oncoming weather conditions before the remainder ofthe platforms in the wind farm. In the embodiment, a platform controllermay, from data it receives from wind direction sensors, determine thatit is the initial platform of the wind farm to experience such oncomingweather condition. The initial platform may then, from sensor dataregarding the conditions it is experiencing, determine the numericalsolution that is appropriate for the wind farm and communicate thatinformation to the remainder of the wind farm. The other controllersthen may direct their respective ballast control systems to achievetheir respective δ_(optimum) from the corresponding simulation.

In an embodiment, a first floating wind turbine platform may send itscurrent weather conditions to one or more other floating wind turbineplatforms, e.g., by the first floating wind turbine platform sendingsuch weather condition data to networked platform controllers onfloating wind turbine platforms within the same wind farm. In response,the first floating wind turbine platform may receive one or more optimumplatform heel angles (δ_(optimum)) from one or more of the otherfloating wind turbine platforms. In the embodiment, the received optimumplatform heel angles may be chosen by the other platform(s) based on acomparison of the weather conditions from the first floating windturbine platform to present or past weather conditions at the otherplatform(s), with the other platforms providing the δ_(optimum) heelangle that platform developed for the weather conditions that mostclosely matched the weather conditions at the first floating windturbine platform. In the embodiment, along with the received δ_(optimum)heel angles, the first floating wind turbine platform may also receivethe associated weather conditions from the other platform, allowing thefirst floating wind turbine platform to choose from among the receivedδ_(optimum) heel angles based on which was developed in response toweather conditions that most closely match the weather conditions at thefirst floating wind turbine platform. In other words, in an embodiment,the δ_(optimum) heel angle (or “vertical target angle”) may betransmitted by another platform in the wind farm which experienced or isexperiencing the same conditions and already performed the optimization.

FIG. 9 illustrates the determination of δ_(optimum) using a numericalsimulation. FIG. 9 is a chart illustrating an example of a determinationof optimum heel angle for a generic 8 MW floating wind turbine with arandom sea state and less-than rated wind speeds over a twenty-five-yearperiod according to an embodiment. In FIG. 9 the computational model wasdeveloped using one defined sea state (random), a standard wind profile,and a fixed offset angle, e.g., fixed offset angle 214, 264, of sixdegrees. FIG. 9 shows the power production for the total time the windspeed of the standard wind profile was at a less-than-rated wind speedfor the 8 MW wind turbine. In this example, determining δ_(optimum) isapproximately 5.4 degrees, which is 10% less than the fixed offsetangle. The determined δ_(optimum) of 5.4 degrees can then be transmittedto the active ballast controller when the actual wind speed and seastate match the model via various feed-forward schemes. One feed-forwardscheme includes a lookup table which gives the optimum angle for a givenset of parameters (e.g., the sea state and wind speed of FIG. 9 , or aset of parameters including sea state, wind direction, and wind speed)with the different optimum angles pre-defined for various combinationsof the parameters in the set. A second feed-forward scheme includes ananalytical function which finds the optimum heel angle δ_(optimum)depending on the input parameters.

FIG. 9 further illustrates that the actual platform heel angle need notexactly match the determined δ_(optimum) heel angle for an embodiment tobe effective. In other words, the error between the determined heelangle and the actual heel angle need not be zero for the inclination ofthe platform to provide improved power production. In FIG. 9 a maximumof approximately 260,500 MWhr are produced at the heel angle of 5.4degrees. However, 99% of that value (or 257,900 MWhr) is produced forinduced platform heel angles of approximately 1.7 degrees and above.That 1.7 degrees is roughly 30% of the 5.4 degrees at which the maximumenergy was produced, and is similarly roughly 30% of the fixed offsetangle of 6 degrees. Considering that 99% of the benefit of inducing aplatform heel angle may be achieved at only 30% of the determinedδ_(optimum) heel angle, in an embodiment it may be sufficient to achievethe determined δ_(optimum) heel angle plus or minus 70% of thedetermined heel angle. Thus, with regard to FIG. 9 and a determinedδ_(optimum) heel angle of 5.4 degrees, resulting induced platform anglesof from 1.6 degrees to 9.2 degrees may be sufficiently close to thedetermined δ_(optimum) heel angle to be acceptable. In an embodiment, anacceptable platform heel angle may be based on a range of angles thatreturn 95% of the benefit of the determined δ_(optimum) heel angle. Inan embodiment, an acceptable platform heel angle may be based on a rangeof angles that return 90% of the benefit of the determined δ_(optimum)heel angle.

FIG. 9 also further illustrates that inclining the platform to make therotor plane more perpendicular to the wind direction at under-rated windspeeds provides improved power production any inclination greater thanzero.

Waves, water depth, and current do not change the mean or angularposition of the platform. This means that the optimum heel angle isindependent from the sea-state. However, the sea-state has an effect onthe dynamics of the platform and turbine. A high sea-state combined witha non-zero mean position (when heeling into the wind) could lead tomotions that could be out of its limitations.

In embodiments determining δ_(optimum) in real time, the data fromsensors in the active ballast controller system (e.g.,inclination-determining sensors, wind speed and direction sensors, powerproduction-determining sensors, and load sensors (e.g., tower loadsensors—sensors measuring the stress at desired locations on theplatform and tower (e.g., bending moment along the tower, or at thetower base) using, e.g., strain gauges)) or in the turbine controllersystem (e.g., power production-determining sensors, thrust loadsensors), or in such systems from other platforms (e.g., a secondplatform from the same wind farm), or in related systems (e.g., powersubstations), or in a combination of such sources may be used. The datamay be used by the active ballast controller through feedbacks schemes.Indeed, when optimally controlled, the power from the system may betracked and controlled and the active ballast controller cancontinuously vary the heel angle in order to optimize the power. Forexample, in an embodiment, power may be optimized by modifying the heelangle. In the embodiment, the platform inclination may be varied usingvarious control algorithms (e.g., PID, Kalman filter, etc.) and theeffect on power generation determined.

In an embodiment, data may be communicated between floating wind turbineplatforms within a wind farm of two or more floating wind turbines or,more simply, between two more floating wind turbines that are situatedsuch that the conditions experienced by one platform may be informativeof or anticipate the conditions experienced by another platform. In theembodiment, power or loading or both may be optimized on a firstplatform by modifying the heel angle and that optimization informationmay be transmitted to one or more of the other platforms. The platformsreceiving the optimization information may include all associatedplatforms, or may be limited by, e.g., those determined to be likely toexperience the same conditions (e.g., wind speed, wind direction, seaconditions) as the optimized platform. The receiving platform may thenimplement the optimized heel angle immediately, or with a timing delayto achieve the optimized heel angle when the conditions associated withthe optimized heel angle are expected to arrive. The receipt of theoptimized heel angle information from the initial platform may reduce oreliminate the time required for the receiving platform to achieve anoptimized heel angle. For example, upon the receiving platform achievingthe optimized heel angle, subsequent feedback control may indicate thatthe received optimized heel angle was, in fact, the optimal heel anglefor the receiving platform. However, the subsequent feedback control mayalso indicate that the received optimized heel angle was, in fact, notoptimal for the receiving platform, in which case the feedback controlcorrectly optimizes the heel angle for the receiving platform. In eithercase, the receiving platform may benefit from receiving the initialoptimized heel angle by reducing the time required for the receivingplatform for determining its own customized, optimized heel angle. Thetime may be reduced because the platform may have only to either confirmthat the received angle was in fact optimal, or to slightly modify thereceived angle to customize it for the receiving platform.

In an embodiment, a machine learning based algorithm combining local andremote information may be used to optimize, for each platform in therelated area, a δ_(optimum) for each platform and optimization time ofeach optimum heel angle for a set of weather conditions. For example,for a wind farm, data may be gathered on weather and sea conditionsexperienced for each of the platforms and the timing of how suchconditions permeated through the wind farm, i.e., the timing andsequence of platforms that experience a weather change and how theweather conditions experienced by the individual platforms is affectedby permeating through the wind farm. Associated data may also begathered on the optimized heel angles (i.e., angle and direction) andtiming for each of the platforms. Sets of such data may be fed tomachine learning-based algorithms to determine optimized heel angles foreach platform in the wind farm, the timing such optimized angles shouldbe achieved, based on an initial set of conditions. In the embodiment,the δ_(optimum) may or may not be the same for any two platforms. Theembodiment may be used to optimize power production for the wind farm asa whole, which might result in one of more of the platforms in the windfarm producing at less-than-optimum power. Similarly, an embodiment maybe used to optimize loading for the wind farm as a whole, which mightresult in one or more of the platforms in the wind farm experiencingless-than-optimal loading. And, in an embodiment that provides aprediction for each individual platform of a time at which the platformshould expect to begin experiencing the predicted conditions,information may be provided to a controller for an individual platform,which may use that information to time the transfer of ballast so thatthe achieving of the optimal inclination (for optimal power or optimalloading or both) coincides with the arrival of the predicted conditions.

In an embodiment, a wind farm will have floating wind turbine platformsat the periphery of the wind farm. Depending on the direction ofoncoming weather conditions, one or more of the peripheral platformswill experience the oncoming weather conditions before the remainder ofthe platforms in the wind farm. In the embodiment, a platform controllermay, from data it receives from wind direction sensors combined withdata indicating the platform's position relative to other platforms ofthe windfarm, determine that it is the initial platform of the wind farmto experience such oncoming weather condition. The initial platform maythen, from sensor data regarding the initial set of conditions that theplatform is experiencing, determine the machine learning based solutionthat is appropriate for the wind farm and communicate that solution tothe remainder of the wind farm. In an embodiment, the initial platformcommunicates the conditions to the remainder of the wind farm and eachother platform of the wind farm then determines the appropriate machinelearning based solution for that set of initial conditions.

FIG. 10 is a chart illustrating capacity factors for a generic 8 MWfixed bottom wind turbine, a generic 8 MW floating wind turbine at evenkeel, and a generic 8 MW floating wind turbine at an optimum heel angleinto the wind according to an embodiment. The capacity factor is thereal power produced by a turbine during 25 years divided by the powerproduced during 25 years if the turbine were always producing itsmaximum power. Comparing capacity factors provides a prediction of theincrease in power production over the turbine lifetime when the platformis inclined to compensate for ε. In FIG. 10 , the base case is afloating platform at even keel. In comparison, the capacity factor of afixed platform shows a 0.25% increase, and the capacity factor of afloating platform at six degrees of heel shows a 0.39% increase. Thus,FIG. 10 shows that not only does heeling the turbine improve powerproduction compared to a floating at even keel turbine, but it alsoimproves power production compared to that of a fixed-bottom turbine.Therefore, the ability of floating platforms with active ballast systemsto change their heel angle allow for an increase in power productioncompared over that produced by wind turbines on fixed foundations. Inother words, the increase in power production of the floating systemover that of the fixed system means that the floating system may be moreefficient in extracting power from the available wind energy than afixed system, even in systems where the actual wind turbines used arethe same. Thus, the control of the platform inclination can have apositive impact on turbine power production, loading, or both, withouthaving to modify or interface with the turbine in any way.

In an embodiment, the various system controllers, e.g., an activeballast controller and a turbine controller, may be separatecontrollers. For example, the turbine controller may be located in theturbine nacelle or tower and the active ballast controller may belocated elsewhere on the floating platform with the two in communicationfor the purposes of, e.g., exchanging data (e.g., wind speed, winddirection, and platform inclination) and commands (e.g., emergency shutdown commands).

In an embodiment, an exchange of data between controllers, e.g., betweenthe active ballast controller and the turbine controller, may instead bereplaced by a command from one controller to the other. For example,when the active ballast controller detects that the inclination of theplatform is beyond a threshold level, the active ballast controller maycommand the turbine controller to shut down or otherwise de-power theturbine. Similarly, when the wind turbine is stopped and the turbinecontroller detects that the wind speed is, or soon will be, sufficientto power the wind turbine, the turbine controller may command the activeballast controller to incline the platform to a certain degree (e.g.,δ_(optimum)).

In an embodiment, the functions of the active ballast controller and theturbine controller may be integrated into a single “global platform”controller, such that data received by the integrated controller isaccessible by aspects of the integrated controller responsible forcontrolling the ballast distribution and accessible by aspects of theintegrated controller responsible for controlling the wind turbine. Insuch an embodiment, data is generally available for the globalcontroller to use as needed, i.e., data is not sent from one aspect ofthe integrated controller to the other. In other words, aspects of theintegrated controller software responsible for controlling the windturbine need not send wind direction and wind speed data to aspects ofthe integrated controller software responsible for ballast distribution.

In an embodiment, active ballast controllers on each floating platformmay exchange data (for example environmental sensors such as wind speed,wind direction, wave height and period, platform heel angle, powerproduced, stress at the base of tower or on specific locations of theplatform) in order to optimize the power and minimize the loads. Thisexchange allows the platform active ballast controller to predict theenvironmental conditions the platform is likely to encounter in the nearfuture and to predict the optimum heel angle which corresponds to theseconditions. In addition, the receipt of an optimized heel angleinformation from an initial platform may reduce or eliminate the timerequired for the receiving platform to achieve an optimized heel angle,as discussed earlier.

In an embodiment, integrated controllers on each floating platform mayexchange data (for example environmental sensors such as wind speed,wind direction, wave height and period, platform heel angle, powerproduced, stress at the base of tower or on specific locations of theplatform) in order to optimize the power and minimize the loads. Thisexchange allows the platform integrated controller to predict theenvironmental conditions the platform will encounter in the near futureand to predict the optimum heel angle which corresponds to theseconditions. In addition, the receipt of an optimized heel angleinformation from an initial platform may reduce or eliminate the timerequired for the receiving platform to achieve an optimized heel angle,as discussed earlier.

In an embodiment, an active ballast system includes pumps and pipingthat move the ballast, e.g., water, between columns. Using data fromsensors (e.g., acceleration sensors, inclination sensors, or both) thecontroller (e.g., a logic board including one or more processors,memory, and instruction incorporated therein) drives the ballast pumpsto set or maintain the desired inclination angle. The pumps may bedriven occasionally, e.g., the controller may turn on the pumps onaverage a few times per day, in order to avoid pump fatigue andexcessive energy expenditures on the platform. This limited driving ofthe pumps may occur despite considerable dynamic changes to the platforminclination angle due to wind and wave disturbances.

In an embodiment, to attain the desired inclination (e.g., δ_(optimum)),the controller determines the optimal heel angle of the platform andadjusts the platform ballast to cause the platform to attain the optimalheel angle, as described. As described in U.S. patent application Ser.Nos. 12/988,121 and 14/283,051, the marine system controller controlsballast water contained inside the three columns of the hull that can bemoved from column to column in order to maintain the low-frequencyplatform angular motions around a predefined equilibrium angle. U.S.patent application Ser. Nos. 12/988,121 and 14/283,051 focus on themethodology to maintain a wind turbine vertical on a floating platform.In comparison, the instant application describes finding a platform heelangle that optimizes power production, reduces loads, or both. Suchchanges to platform heel angle are achievable provided the floatingplatform is equipped with an active ballast system, aspects of whichwill now be described in further detail.

In an embodiment, data communicated between active ballast controllersand integrated controllers present in a wind farm allows a controller ona particular platform to predict the future site conditions on thatplatform and allows the controller to time a pre-ballast so that theplatform is at the optimized heel angle upon the arriving of theanticipated conditions. In an embodiment, the pre-ballast may be timedso that the platform achieves the optimized heel angle at a timecoinciding with the arrival of the anticipated conditions. Such apre-ballasting embodiment may reduce the time between the arrival of theanticipated conditions and the time the optimized heel angle isachieved. A machine learning based algorithm combining local and remoteinformation, as described above, may also be used to optimize theplatform heel angle and optimization time of each optimum heel angle. Inan embodiment, data communicated between active ballast controllers andintegrated controllers present in a wind farm may allow a controller ona particular platform to predict the future site conditions on thatplatform and optimize the heel angle, where the optimal heel angle isdetermined by considering the energy gained by heeling into the windversus the energy used by the active ballast pumps. For example, in asite where the wind direction or speed is changing rapidly, a controllermay decide to heel less into the wind order to be prepared for suddenwind characteristic changes. A machine learning based algorithmcombining local and remote information, as described above, may also beused to optimize the platform heel angle and optimization time of eachoptimum heel angle.

FIG. 11A is a flow chart of an embodiment of a method 1100 forcontrolling an inclination of a first floating wind turbine platform tooptimize power production. In FIG. 11A, the floating wind turbineplatform may include: a generator connected to a shaft having a shaftlongitudinal axis; a set of turbine blades connected to the shaft anddefining a blade plane that is perpendicular to the shaft longitudinalaxis; a tower having a tower longitudinal axis, the shaft beingconnected to the tower such that there is a non-zero angle between theblade plane and the tower longitudinal axis; at least three stabilizingcolumns, each of the at least three stabilizing columns having aninternal volume for containing ballast; and a ballast system fordistributing ballast, the first floating wind turbine platform having arated wind speed, a minimum wind speed, and a floating position in whichthe tower longitudinal axis is vertical. In method 1100, in step 1105, acontrol software module executing on a processor of the ballast systemreceives inclination data associated with an inclination of the firstfloating wind turbine platform. In step 1110, the control softwaremodule receives first wind speed data and first wind direction data. Instep 1115, the control software module determines a platform wind speedusing the first wind speed data. In step 1120, the control softwaremodule determines, using the first wind direction data, an angle ofdifference between the shaft longitudinal axis and a wind direction, theangle of difference having a vertical component relative to a horizontalplane. In step 1125, when the platform wind speed is below the minimumwind speed, the control software module causes the ballast system todistribute ballast to maintain the first floating wind turbine platformat the floating position. And in step 1130, when the platform wind speedis greater than the minimum wind speed and less that the rated windspeed, the control software module causes the ballast system todistribute ballast to reduce the vertical component of the angle ofdifference to a first vertical target angle chosen to optimize powerproduced by the generator.

FIG. 11B is a flow chart of an embodiment of a method 1150 forcontrolling an inclination of a first floating wind turbine platform tooptimize power production. In FIG. 11B, the floating wind turbineplatform may include: a generator connected to a shaft having a shaftlongitudinal axis; a set of turbine blades connected to the shaft anddefining a blade plane that is perpendicular to the shaft longitudinalaxis; a tower having a tower longitudinal axis, the shaft beingconnected to the tower such that there is a non-zero angle between theblade plane and the tower longitudinal axis; at least three stabilizingcolumns, each of the at least three stabilizing columns having aninternal volume for containing ballast; and a ballast system fordistributing ballast, the first floating wind turbine platform having arated wind speed, a minimum wind speed, and a floating position in whichthe tower longitudinal axis is vertical. In method 1150, in step 1155, acontrol software module executing on a processor of the ballast systemreceives inclination data associated with an inclination of the firstfloating wind turbine platform. In step 1160, the control softwaremodule receives first wind speed data and first wind direction data. Instep 1165, the control software module determines a platform wind speedusing the first wind speed data. In step 1170, the control softwaremodule determines, using the first wind direction data, an angle ofdifference between the shaft longitudinal axis and a wind direction, theangle of difference having a vertical component relative to a horizontalplane. In step 1175, when the platform wind speed is below the minimumwind speed, the control software module causes the ballast system todistribute ballast to maintain the first floating wind turbine platformat the floating position. And in step 1180, when the platform wind speedis greater than the minimum wind speed, the control software modulecauses the ballast system to distribute ballast to reduce the verticalcomponent of the angle of difference to a first vertical target anglechosen to optimize power produced by the generator.

FIG. 12 shows a floating wind turbine platform 1200 with decoupledmarine system 1205 and wind turbine controllers 1210. For moreredundancy and for a more efficient system, two pumps can be installedat each of the first column 1215, second column 1220, and third column1225, which would bring the total number of pumps for the system to sixpumps (1230, 1235, 1240, 1245, 1250, and 1255). Each of the six pumpsmay transfer ballast 1260 from the column at which the pump resides tothe column to which the pump is connected.

For example, the first column 1215 has two pumps: pump 1230 and pump1235. The pumps work on an on-and-off basis. They are switched on onlyoccasionally, e.g., when the wind speed or direction changessignificantly, to attain the desired platform inclination. Thecontroller is optimally set to turn on the pumps on average a few timesper day, despite considerable dynamics due to wind and wave disturbance,in order to avoid pump fatigue and excessive energy expenditures on theplatform.

The platform is fitted with motion sensors 1265 to measure the platformangular motions that can be used as input signals for the marine systemcontroller. Accelerometers or inclinometers may be composed of a simplemoving mass mounted on springs that track gravity. They both sense theacceleration due to the rotation of the platform, but also due to thelinear accelerations—in surge, sway, and heave.

As far as this marine system controller is concerned, both a bi-axialpitch-and-roll inclinometer or a bi-axial surge-and-sway accelerometerare acceptable since linear accelerations (surge and sway) can betransformed to angular motions (pitch and roll). Both sensors areacceptable so long they track the gravity component of the platform,which is similar to the low-frequency angular motions. These motionssensors can be installed at any location on the platform. Usually forredundancy again, several motion sensors are installed in differentcolumns and their measurement outputs are compared at all times beforebeing fed into the control loop.

FIG. 14 is a flow chart for controlling a floating platform according toan embodiment. In FIG. 14 , the platform roll angle (α) and pitch angle(β) signals are provided by the platform sensors and input to thecontroller. In an embodiment, the measured roll and pitch angle signalsare low-pass filtered (α and β) to remove high-frequency disturbances,such as, e.g., those resulting from the wave and wind dynamic andstochastic effects. In an embodiment, the platform roll and pitch anglesare low-pass filtered by a signal processing 1420 using standardlow-pass filtering strategies such as high-order Butterworth filters. Inan embodiment, the filtering may be performed in advance of thecontroller receiving the signals. And in an embodiment, the filteringmay be performed by software or hardware components of the controlleritself.

FIG. 14 shows the logic behind the feedback controller. The filteredplatform roll and pitch angles, α and β, are input signals to thecontroller at 1405, provided by the platform sensors. Firstly, themeasured signals are low-pass filtered at 1420 as discussed. Based onthe filtered platform pitch and roll angles, α and β, the relativeangles θ_(i-j) between column top centers i and j, are derived usingEquations 6A, 6B, 6C for a platform with columns at the vertices of anisosceles or equilateral triangle.

The following convention is used. If θ_(i-j) is positive, it means thatcolumn i is higher than column j. The error determined using Equation 7is the error used as an input of the controller. Based on the sign ofthe error, e_(i-j), the correct pump P_(i-j) will be turned on at 410provided that e_(i-j) is greater than a certain value that defines thedead-band for ON. The pumps P_(i-j) or P_(j-i) will be switched offprovided that e_(i-j) is less than a certain value that defines thedead-band for OFF. Depending on the relative angles θ_(i-j), one, two,or three pumps will be on. With this algorithm based on the relativeangles between column top centers, the fastest water transfer path isalways considered, thus the platform attains the desired angle veryquickly or as fast as possible in every situation. Automatic bypass isalso functioning with that approach, if one pump is suddenly deficient.The platform dynamics are measured, including its roll and pitch angles,α and β, at 1415 and used to provide a heel angle measurement fed backinto the feedback loop.

A standard Proportional-Integral-Derivative (PID) controller could alsobe used in the determination of based on the heel angle error, but asimple on-off controller preceded by a filtered signal can besufficient, due to the high capacitance of the system.

The wind turbine controller includes a number of instruments, a numberof actuators, and a computer system (or a microprocessor) able toprocess the signals input by the instruments and communicate thesesignals to the actuators. The main objective of the wind turbinecontroller is the maximization or generation of the power production andthe minimization or reduction of the extreme loads on the wind turbinecomponents. In an embodiment, the features of a wind turbine controllermay be incorporated into an integrated controller.

Two types of control are usually performed by the system. Thesupervisory control allows the turbine to go from one operational stateto the other. Examples of operational states are start-up, powerproduction, normal shutdown, emergency shutdown, standby, and so forth.

The second type of control performed by a wind turbine is calledclosed-loop control and occurs at a given operational state of theturbine to keep the turbine at some defined characteristic oroperational boundary for that state.

The wind turbine thrust force F_(T), the aerodynamic torque T_(r), andthe power P_(r) vary according to:

$\begin{matrix}\left\{ \begin{matrix}{F_{T} = {\frac{1}{2}\rho\;{{AC}_{T}\left( {\lambda,\Delta} \right)}V^{2}}} \\{T_{r} = {\frac{1}{2}\rho\;{{ARC}_{q}\left( {\lambda,\Delta} \right)}V^{2}}} \\{P_{r} = {\frac{1}{2}\rho\;{{AC}_{p}\left( {\lambda,\Delta} \right)}V^{3}}}\end{matrix} \right. & {{{Equations}\mspace{14mu} 12A},{12B},{12C}}\end{matrix}$

Where ρ is the density of air, R is the rotor radius, A is the apparentrotor swept area (Equation 2), V is the wind speed, C_(T) is the thrustcoefficient, C_(q) is the torque coefficient, and Cp is the powercoefficient. All the non-dimensional coefficients (C_(T), C_(q), and Cp)depend on three parameters, the speed-tip ratio λ, the blade pitch angleΔ, and the global offset angle ε. The speed-tip ratio is the ratio ofthe angular speed of the rotor ω at the tip of the blade over the windspeed V.

Typically, in power production mode, depending on the wind speed, twocontrol regions called partial load and full load require differentcontrol strategies.

In partial load, when the wind speed is below the rated wind speed—thelowest wind speed at which the turbine produces the maximum power—thecontroller will vary the generator torque to maximize the aerodynamicpower capture, while keeping the blade pitch angle Δ at its optimalsetting.

Basically, the generator torque can be controlled to any desired value,which is proportional to the square of the filtered generator speed,with the aim of varying the rotor rotational speed to maintain aconstant and optimal tip-speed ratio λ.

During power production, sudden variations of wind speed or directionscan occur quite often at the site of floating wind turbines. Thesevariations directly impact the overall magnitude and direction of thethrust force of the turbine applied to the rotor disk area in thedirection of the wind. Viewed from the supporting platform far below thewind turbine hub, the thrust force represents an overturning moment tobe withstood, and can yield high platform heel angles. Even iftemporary, these high heel angles are detrimental to the overall systemdesign life, and should be minimized during the unit lifetime.

In an embodiment, an integrated controller controls the wind turbine andthe ballast pump simultaneously, in order to maintain the platform heelangle below a certain limit at all times or as desired. This controllermay have platform control features integrated into a wind turbinecontroller modified to interact directly with the ballast pumps tominimize the heel angles of the floatation frame. A benefit brought bythis is a rise in the structural design life of the floatation frame ifthe same amount of construction material (most of the case, it is steel)is used, without sacrificing the overall power output of the turbine.

Based on industry experience, heel angles of up to 15 degrees could bereached by a floating wind turbine platform when the maximum thrust ofthe wind turbine is applied at the hub height. If the two controllersare decoupled, as described with regard to FIG. 12 , the platform marinesystem controller works independently of the wind turbine. A simplesignal can be shared between the two controllers to shut down theturbine if a fault occurs on the platform.

If the two control systems are completely decoupled, the platform willexperience high heel angles in sudden shifts of wind speed or direction.The reason lies behind the difference in time constants for the twocontrol systems. The turbine controller usually acts very quickly on thescale of a second, since it is designed to adapt to the quickdisturbances of wind speed due to turbulence. The marine systemcontroller is working on a timeframe of about ten minutes, because ofthe time necessary to pump water from one column to another.

For example, if the wind shifts from the cut-in wind speed to the ratedwind speed in a matter of minutes, an extreme heel angle of about 15degrees could be experienced by the floating platform, until the marinesystem controller triggers the appropriate ballast pumps to bring theplatform back to even keel. At this high heel angle, the power output ofthe turbine would be reduced by the cosine of the heel angle of 15degrees, since the rotor swept area is reduced because the blade planeis not perpendicular to the wind, as discussed earlier.

Thus, a platform high heel angle results in some loss in turbine poweroutput. So, the marine system controller, even if used independently ofthe turbine controller, presents the benefit of keeping the tower at thedesired alignment most of the time, but high heel angles are stillexperienced during transients (such as turbine startups or shutdowns) orsudden shifts of wind speed or wind direction.

FIG. 13 shows a floating wind turbine platform 1300 with an integratedfloating wind turbine and platform controller 1305. In a specificembodiment of this invention, the wind turbine and platform controller1305 directly controls the platform pumps (1330, 1335, 1340, 1345, 1350,and 1355), in order to remedy the issues presented by two decoupledcontrollers. The platform pitch and roll angle information obtained bymotion sensors 1365 can be used directly by the turbine controller tokeep the platform heel angle at, or within a desired range of a targetinclination (see the discussion with regard to FIG. 10 ), at all timesor as desired.

The wind turbine controller 1305 would control either the generatortorque or the blade pitch angle (or both at the same time). Thus, as anexample of integrated control of both the wind turbine and the platform,integrated wind turbine controller 1305 may temporarily maintain thethrust of the turbine 1310 at a lower level, while water is being pumpedfrom between the three columns (1315, 1320, and 1325). In other words,the change of thrust loading on the turbine 1310 resulting in anoverturning moment will match or correspond to the change of rightingmoment due to the ballast water.

During that transition period—when the water 1360 is being pumped fromcolumn to column—the overall thrust and power output of the turbinecould be lower, but the platform heel angle would also be lower andcloser to the target angle, which would actually keep the powerproduction higher, than if the platform heel angle was 15 degrees.

There is clearly a tradeoff between the platform maximum allowable heelangle and the power production. If the heel angle is kept too low, thechange in thrust will be very small while water is being pumped, leadingto a lower power output than if the ballast pumps were started after thechange in thrust. If the heel angle is kept too high, the power outputloss originates from the cosine term. In other words, an optimal pointcan be found at which the power production would be maximized at alltimes or sufficiently high, while the low-frequency platform heel anglewould be kept low, leading to an increase in the design life of theplatform (due to a reduction in cyclic low frequency loads caused by theweight of the rotor nacelle assembly in high heel angles).

However, in many cases, the main benefit of this system is truly thereduced amount of construction material for the platform, such as steel,which will improve the cost-effectiveness of floating wind turbinetechnologies.

In an embodiment, this integrated controller entails the modification ofa conventional wind turbine controller to control the aerodynamic torque(or thrust force) of the wind turbine while allowing the activation ofappropriate ballast water pumps.

Equations 12A, 12B, and 12C suggest that the thrust and the aerodynamictorque can be reduced if either the tip-speed ratio or the blade pitchare modified (or both at the same time). Therefore, these two parameterscan be changed by the controller in partial load and in full load tomaintain an aerodynamic torque that would minimize or reduce theplatform heel angle.

At this stage, several options are considered depending on theoperational state and the region of control for the wind turbine. Forsmall angles, the platform heel angle h is a combination of roll andpitch and is defined as the squares root of the sum of the roll andpitch angles squared.h=√{square root over (α²+β²)}  Equation 13

In an embodiment, in a first form, the generator torque demand could beadjusted to modify the tip-speed ratio λ or the rotor speed, in order toreduce the aerodynamic thrust when the platform heel exceeds a certainset point. The appropriate pumps could then be started up by the controlsystem, and the torque demand would be constantly adjusted, until thepumps are turned off, and normal operation can restart.

During that transition period, the generator torque would be partiallycontrolled based on the platform heel angles measured from theinclinometers or accelerometers. The conventional wind component of thegenerator torque is obtained through a direct measurement and low-passfiltering of the rotor velocity. With this strategy in mind, the torqueof the turbine would be derived as a sum of two terms, one due to theplatform heel, and one due to wind-induced conventional rotor velocity.

If the platform reaches a heel angle greater than a given set point (forexample 5 degrees), this new control loop is called by the system.Automatically, the right pumps are switched on, while the desired torquewould be calculated slightly differently to temporarily reduce the rotoraerodynamic torque (or thrust). This control loop comprises twobranches.

FIG. 15 shows a flowchart for an integrated controller with amodification of the control loop of FIG. 14 . The modification includesthe control of the rotor velocity in which generator speed (or rotorvelocity) is first used as an input, low-pass filtered, and thegenerator torque is determined based on a formula or lookup table.Usually, the generator torque is directly proportional to the filteredrotor velocity squared. The aerodynamic torque T_(R) is an input to thecontroller, and will always try to be matched by the generator torqueT_(G) command, based on the actual rotor velocity ω. The rotor inertia J1505, and an integrator block 1510 come into play to represent thedynamic of the system described by Equation 14:T _(R) −T _(G) =J{dot over (ω)}  Equation 14

In full load, or above rated wind speed, the power produced is close tothe rated power, but the turbine must limit or reduce the aerodynamicpower extraction (or the Cp coefficient) so as not to exceed turbinecomponent design loads, such as the generator. This time, the rotorspins at a constant angular speed ω, so the only parameter that canreduce the power coefficient Cp is the blade pitch angle Δ.

The generator torque is also held constant at the rated torque, butcould also be controlled. The additional aerodynamic power that could beextracted is thus shed by varying the blade pitch angle. An increase inblade pitch angle—when the leading edge of the blade is turned into thewind—diminishes the aerodynamic torque by decreasing the angle ofattack, hence the lift on the blades. Here, conventional PI or PIDcontrol strategies are used to modify the blade pitch angle, based onthe generator speed error between the filtered generator speed and therated generator speed. In some cases, notch filters are used to preventexcessive controller actions at the natural frequency of certain turbinecomponents, such as the drivetrain torsional frequency or the bladepassing frequency.

The control loop is otherwise as described with reference to FIG. 14 anduses the platform roll and pitch angles as input signals, calculates theheel angle of the platform in the frame of reference of the nacelleturned into the wind, low-pass filters this heel angle, and finallycomputes the second component of the desired torque using a PIDcontroller 1515 based on the platform heel angle error.

FIG. 16 shows a flowchart for an integrated controller with amodification of the standard blade pitch control loop in which the rotorvelocity ω is measured, properly filtered and processed by 1630, andcompared to its setpoint ω_(ref) (the rotor velocity at rated power),which creates an error signal. This rotor speed error signal is fed intoa PI controller 1615 to compute the pitch command sent to the bladepitch actuator 1620. The wind turbine 1625 continues to operate as theblade pitch angles are being controlled.

During a turbine startup, the PI controller 1615 sends a command to theblade pitch actuator 1620 to pitch the blades from feather (90 degrees)to the run position and let the wind accelerate the rotor until acertain speed is reached. The generator is then engaged and the windturbine 1625 starts producing power.

Similarly, for a normal turbine shutdown, the blades are pitched fromtheir run position to feather. The generator is disengaged, when theturbine slows enough to drop the power to zero.

As shown in FIG. 16 , the blade pitch angle may also be modified tocontrol the aerodynamic torque. The blade pitch command is computedbased on the sum of the typical filtered rotor speed error componentcalculated with a PID controller 1615, and a second component based onthe platform heel angle error calculated again with a PID controller1605. The new pitch command is the sum of these two components only ifthe platform error exceeds a certain band of heel angle about theoptimum angle δ_(optimum) (for example+/−1, 2, or 5 degrees aroundδ_(optimum)). In that case again, the controller presents a control loopwith two branches, one branch dealing with the component based on thefiltered rotor speed error, the other branch taking care of the othercomponent based on the filtered platform heel angle error.

In an embodiment, a combination of these two forms of control isprovided for both regions of turbine operation, in partial load and infull load. The modification of both the generator torque 1610 and theblade pitch angle in both regions would add flexibility in the controlsystem, regardless of the control region. For certain types of turbine,it is already not atypical to see the blade pitch angle being controlledbelow rated wind speed, and the generator torque being controlled aboverated wind speed.

Thus, on the same principle, the generator torque controller in thefirst form and the blade pitch controller in the second form could becombined to temporarily control the aerodynamic torque, while the wateris being shifted from column to column. The combination of bothstrategies would improve the overall performance of this integratedcontroller.

Gentle startup and shutdowns procedures are definitively desirable, asthey can be intense fatigue life drainers for the turbine and thefloatation frame. In a specific embodiment, a feature of the inventionalso relates to a controller that is used in the case of startup andshutdowns on the same principles as the ones described in operation.

In the case of a startup, the blade pitch may be controlled to go fromfeather-to-pitch at the same speed as the ballast water is moved fromcolumn to column, so that the heel angle of the platform remains at ornear the target angle at all times during the procedure. In the case ofa shutdown, the blades would be controlled to go from pitch-to-featherwhile allowing the ballast water to maintain the platform at or near thetarget angle, until the turbine is stopped.

In both cases, the filtered platform heel angle error could be used asan input to an extra branch in the control loop to calculate the bladepitch at all times. As a result, the blade pitch increase or decrease ismuch slower than in the case of a conventional controller. Similarly,the generator torque ramp-up or ramp-down time could be increased tomatch the required ballasting time, in order to minimize or reduce theplatform heel angle error at all times or as desired during startup andshutdowns. Again, a combination of blade pitch and torque control can beused simultaneously to produce the same intended results.

In an embodiment, the decoupled marine system 1205 and wind turbinecontrollers 1210, or integrated wind turbine and platform controller1305 may receive information allowing the controller to anticipate achange in wind speed or direction at the wind turbine. Such ananticipated change may, for example, trigger a startup or shutdown ofthe turbine, or prompt the controller to adjust the turbine yaw to pointthe turbine into the anticipated wind direction. In either case, beforethe actual arrival of the anticipated wind change, the controller maypre-transfer water from column to column before any turbine action isperformed. For instance, in the case of a turbine shutdown, the platformmay be pre-inclined while the turbine is still spinning, so that half ofthe water ballast transfer is done upfront. The turbine would then beshut down, and the ballast water would continue to be transferredbetween columns until the platform is at or near the target angle.

The embodiment may be used to improve power production as well when thewind turbine or floating platform detects any significant anticipatedchange in wind speed or direction. In advance of correcting yaw or bladepitch or both, ballast water may be pre-adjusted in the platformcolumns, so that the error in the heel angle experienced by the platformwith the eventual change in the wind speed or direction may be reduced.At all times or as desired, the amount of water in the different columnscan be estimated based on the thrust force of the turbine and itsapplied direction, or based on the wind speed and the wind direction.Using such information, information, a look-up table may be derived thatthe controller could consult to pre-adjust the ballast water of theplatform to anticipate the wind change and reduce the error in theplatform inclination caused by the wind change.

Thus, in this embodiment, the controller may use two extra inputsignals: an estimate of the anticipated wind speed and anticipated winddirection. A pre-compensation algorithm would be applied to pre-adjustthe amount of ballast water in the different columns. Instruments suchas anemometers or Light Detection and Ranging or Laser Imaging Detectionand Ranging (LIDAR) sensors can be installed for that purpose.

This strategy leads to two possibilities: it could be a complementaryapproach to refine the first integrated controller described in theprevious section (more information comes from the wind measurements), orit could be a much simpler integrated controller decoupled with existingwind turbine control schemes (variable torque and pitch controllers),and therefore could be implemented in a much easier fashion.

FIG. 17 conceptually illustrates an example electronic system 1700 withwhich some embodiments may be implemented. Electronic system 1700 can bea computer, phone, PDA, or any other sort of electronic device. Such anelectronic system includes various types of computer readable media andinterfaces for various other types of computer readable media.Electronic system 1700 includes a bus 1708, processing unit(s) 1712, asystem memory 1704, a read-only memory (ROM) 1710, a permanent storagedevice 1702, an input device interface 1714, an output device interface1706, and a network interface 1716.

Bus 1708 collectively represents all system, peripheral, and chipsetbuses that communicatively connect the numerous internal devices ofelectronic system 1700. For instance, bus 1708 communicatively connectsprocessing unit(s) 1712 with ROM 1710, system memory 1704, and permanentstorage device 1702.

From these various memory units, processing unit(s) 1712 retrievesinstructions to execute and data to process in order to execute theprocesses of the subject disclosure. The processing unit(s) can be asingle processor or a multi-core processor in different embodiments.

ROM 1710 stores static data and instructions that are needed byprocessing unit(s) 1712 and other modules of the electronic system.Permanent storage device 1702, on the other hand, is a read-and-writememory device. This device is a non-volatile memory unit that storesinstructions and data even when electronic system 1700 is off. Someembodiments of the subject disclosure use a mass-storage device (such asa magnetic or optical disk and its corresponding disk drive) aspermanent storage device 1702.

Other embodiments use a removable storage device (such as a floppy disk,flash drive, and its corresponding disk drive) as permanent storagedevice 1702 Like permanent storage device 1702, system memory 1704 is aread-and-write memory device. However, unlike storage device 1702,system memory 1704 is a volatile read-and-write memory, such as randomaccess memory. System memory 1704 stores some of the instructions anddata that the processor needs at runtime. In some embodiments, theprocesses of the subject disclosure are stored in system memory 1704,permanent storage device 1702, and/or ROM 1710. For example, the variousmemory units include instructions for controlling an inclination of afloating wind turbine platform in accordance with some embodiments. Fromthese various memory units, processing unit(s) 1712 retrievesinstructions to execute and data to process in order to execute theprocesses of some embodiments.

Bus 1708 also connects to input and output device interfaces 1714 and1706. Input device interface 1714 enables the user to communicateinformation and select commands to the electronic system. Input devicesused with input device interface 1714 include, for example, alphanumerickeyboards and pointing devices (also called “cursor control devices”).Output device interface 1706 enables, for example, the display of imagesgenerated by the electronic system 1700. Output devices used with outputdevice interface 1706 include, for example, printers and displaydevices, such as cathode ray tubes (CRT) or liquid crystal displays(LCD). Some embodiments include devices such as a touchscreen thatfunctions as both input and output devices.

Finally, as shown in FIG. 17 , bus 1708 also couples electronic system1700 to a network (not shown) through a network interface 1716. In thismanner, the computer can be a part of a network of computers, such as alocal area network, a wide area network, or an Intranet, or a network ofnetworks, such as the Internet. Any or all components of electronicsystem 1700 can be used in conjunction with the subject disclosure.

Many of the above-described features and applications are implemented assoftware processes that are specified as a set of instructions recordedon a computer readable storage medium (also referred to as computerreadable medium). When these instructions are executed by one or moreprocessing unit(s) (e.g., one or more processors, cores of processors,or other processing units), they cause the processing unit(s) to performthe actions indicated in the instructions. Examples of computer readablemedia include, but are not limited to, CD-ROMs, flash drives, RAM chips,hard drives, EPROMs, etc. The computer readable media does not includecarrier waves and electronic signals passing wirelessly or over wiredconnections.

In this specification, the term “software” is meant to include firmwareresiding in read-only memory or applications stored in magnetic storage,which can be read into memory for processing by a processor. Also, insome embodiments, multiple software aspects of the subject disclosurecan be implemented as sub-parts of a larger program while remainingdistinct software aspects of the subject disclosure. In someembodiments, multiple software aspects can also be implemented asseparate programs. Finally, any combination of separate programs thattogether implement a software aspect described here is within the scopeof the subject disclosure. In some embodiments, the software programs,when installed to operate on one or more electronic systems, define oneor more specific machine embodiments that execute and perform theoperations of the software programs.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, declarative orprocedural languages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, object, orother unit suitable for use in a computing environment. A computerprogram may, but need not, correspond to a file in a file system. Aprogram can be stored in a portion of a file that holds other programsor data (e.g., one or more scripts stored in a markup languagedocument), in a single file dedicated to the program in question, or inmultiple coordinated files (e.g., files that store one or more modules,sub programs, or portions of code). A computer program can be deployedto be executed on one computer or on multiple computers that are locatedat one site or distributed across multiple sites and interconnected by acommunication network.

These functions described above can be implemented in digital electroniccircuitry, in computer software, firmware or hardware. The techniquescan be implemented using one or more computer program products.Programmable processors and computers can be included in or packaged asmobile devices. The processes and logic flows can be performed by one ormore programmable processors and by one or more programmable logiccircuitry. General and special purpose computing devices and storagedevices can be interconnected through communication networks.

Some embodiments include electronic components, such as microprocessors,storage and memory that store computer program instructions in amachine-readable or computer-readable medium (alternatively referred toas computer-readable storage media, machine-readable media, ormachine-readable storage media). Some examples of such computer-readablemedia include RAM, ROM, read-only compact discs (CD-ROM), recordablecompact discs (CD-R), rewritable compact discs (CD-RW), read-onlydigital versatile discs (e.g., DVD-ROM, dual-layer DVD-ROM), a varietyof recordable/rewritable DVDs (e.g., DVD-RAM, DVD-RW, DVD+RW, etc.),flash memory (e.g., SD cards, mini-SD cards, micro-SD cards, etc.),magnetic and/or solid state hard drives, read-only and recordableBlu-Ray™ discs, ultra density optical discs, any other optical ormagnetic media, and floppy disks. The computer-readable media can storea computer program that is executable by at least one processing unitand includes sets of instructions for performing various operations.Examples of computer programs or computer code include machine code,such as is produced by a compiler, and files including higher-level codethat are executed by a computer, an electronic component, or amicroprocessor using an interpreter.

While the above discussion primarily refers to microprocessor ormulti-core processors that execute software, some embodiments areperformed by one or more integrated circuits, such as applicationspecific integrated circuits (ASICs) or field programmable gate arrays(FPGAs). In some embodiments, such integrated circuits executeinstructions that are stored on the circuit itself.

As used in this specification and any claims of this application, theterms “computer”, “server”, “processor”, and “memory” all refer toelectronic or other technological devices. These terms exclude people orgroups of people. For the purposes of the specification, the termsdisplay or displaying means displaying on an electronic device. As usedin this specification and any claims of this application, the terms“computer readable medium” and “computer readable media” are entirelyrestricted to tangible, physical objects that store information in aform that is readable by a computer. These terms exclude any wirelesssignals, wired download signals, and any other ephemeral signals.

To provide for interaction with a user, embodiments of the subjectmatter described in this specification can be implemented on a computerhaving a display device, e.g., a CRT (cathode ray tube) or LCD (liquidcrystal display) monitor, for displaying information to the user and akeyboard and a pointing device, e.g., a mouse or a trackball, by whichthe user can provide input to the computer. Other kinds of devices canbe used to provide for interaction with a user as well; for example,feedback provided to the user can be any form of sensory feedback, e.g.,visual feedback, auditory feedback, or tactile feedback; and input fromthe user can be received in any form, including acoustic, speech, ortactile input. In addition, a computer can interact with a user bysending documents to and receiving documents from a device that is usedby the user; for example, by sending web pages to a web browser on auser's client device in response to requests received from the webbrowser.

Embodiments of the subject matter described in this specification can beimplemented in a computing system that includes a back end component,e.g., as a data server, or that includes a middleware component, e.g.,an application server, or that includes a front end component, e.g., aclient computer having a graphical user interface or a web browserthrough which a user can interact with an embodiment of the subjectmatter described in this specification, or any combination of one ormore such back end, middleware, or front end components. The componentsof the system can be interconnected by any form or medium of digitaldata communication, e.g., a communication network. Examples ofcommunication networks include a local area network and a wide areanetwork, an inter-network (e.g., the Internet), and peer-to-peernetworks (e.g., ad hoc peer-to-peer networks).

The computing system can include clients and servers. A client andserver are generally remote from each other and typically interactthrough a communication network. The relationship of client and serverarises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other. In someembodiments, a server transmits data (e.g., an HTML page) to a clientdevice (e.g., for purposes of displaying data to and receiving userinput from a user interacting with the client device). Data generated atthe client device (e.g., a result of the user interaction) can bereceived from the client device at the server.

The following paragraphs contain enumerated embodiments of theinvention.

1. A method for controlling an inclination of a first floating windturbine platform to optimize power production, the first floating windturbine platform including: a generator connected to a shaft having ashaft longitudinal axis; a set of turbine blades connected to the shaftand defining a blade plane that is perpendicular to the shaftlongitudinal axis; a tower having a tower longitudinal axis, the shaftbeing connected to the tower such that there is a non-zero angle betweenthe blade plane and the tower longitudinal axis; at least threestabilizing columns, each of the at least three stabilizing columnshaving an internal volume for containing ballast; and a ballast systemfor distributing ballast, the first floating wind turbine platformhaving a rated wind speed, a minimum wind speed, and a floating positionin which the tower longitudinal axis is vertical, the method comprising:receiving, by a control software module executing on a processor of theballast system, inclination data associated with an inclination of thefirst floating wind turbine platform; receiving, by the control softwaremodule, first wind speed data and first wind direction data;determining, by the control software module using the first wind speeddata, a platform wind speed; determining, by the control software moduleusing the first wind direction data, an angle of difference between theshaft longitudinal axis and a wind direction, the angle of differencehaving a vertical component relative to a horizontal plane; causing, bythe control software module when the platform wind speed is below theminimum wind speed, the ballast system to distribute ballast to maintainthe first floating wind turbine platform at the floating position; andcausing, by the control software module when the platform wind speed isgreater than the minimum wind speed and less that the rated wind speed,the ballast system to distribute ballast to reduce the verticalcomponent of the angle of difference to a first vertical target anglechosen to optimize power produced by the generator.

2. The method of claim 1 further comprising: receiving, by the controlsoftware module, the first vertical target angle from a second floatingwind turbine platform.

3. The method of claim 2 further comprising: receiving, by the controlsoftware module from the second floating wind turbine platform, secondwind speed data and second wind direction data; and comparing, by thecontrol software module, the second wind speed data to the first windspeed data and the second wind direction data to the first winddirection data, wherein the ballast system is caused to distributeballast to reduce the vertical component of the angle of difference tothe received first vertical target angle when both: the platform windspeed is greater than the minimum wind speed and less that the ratedwind speed; and the comparison indicates the first wind speed is withina first threshold from the second wind speed and the first winddirection is within a second threshold from the second wind direction.

4. The method of claim 2, wherein the first vertical target angle isreceived from the second wind turbine platform in response to the secondfloating wind turbine platform receiving the first wind speed data andthe first wind direction data.

5. The method of claim 1, wherein the first vertical target angle is achosen vertical target angle selected from among a plurality ofpotential vertical target angles in a numerical look-up table, thechosen vertical target angle selected based on at least one from thegroup: first wind speed, first wind direction, sea state, platformmotion, and turbine motion.

6. The method of claim 1, wherein the first vertical target angle is acomputed vertical target angle computed as a function of at least onefrom the group: first wind speed, first wind direction, sea state,platform motion, and turbine motion.

7. The method of claim 1 further comprising: receiving, by the controlsoftware module executing on the processor, first power data regardingpower produced by the generator when the platform is inclined at thefirst vertical target angle; modifying, by the control software module,the first vertical target angle to a second vertical target angle;receiving, by the control software module, second power data regardingpower produced by the generator when the platform is inclined at thesecond vertical target angle; and maintaining, by the control softwaremodule, the inclination of the first floating wind turbine platform atthe second vertical target angle when the second power data is greaterthan the first power data.

8. The method of claim 1, wherein: the first wind speed data and firstwind direction data represent wind conditions at a location a distancefrom the first floating wind turbine platform; the determining theplatform wind speed uses the first wind speed data, the first winddirection data, the location, and the distance; the platform wind speedis an estimation of wind speed at the platform at a future time; and thevertical component relative to the horizontal plane is an estimate ofthe vertical component at the future time; the method furthercomprising: estimating, by the control software module based on thevertical component, a preparation amount of time required by the ballastsystem to reduce the vertical component to the first vertical targetangle, wherein: the causing, by the control software module when theplatform wind speed is greater than the minimum wind speed and less thatthe rated wind speed, the ballast system to distribute ballast to reducethe vertical component of the angle of difference to a first verticaltarget angle chosen to optimize power produced by the generatorincludes: causing, by the control software module when the platform windspeed is greater than the minimum wind speed and less that the ratedwind speed, the ballast system to begin to distribute ballast to reducethe vertical component of the angle of difference to the first verticaltarget angle the preparation amount of time in advance of the futuretime.

9. A non-transitory computer-readable medium comprising instructionsstored therein according to any of enumerated embodiments 1-8.

10. A ballast system for distributing ballast for controlling aninclination of a floating wind turbine platform to optimize powerproduction, the floating wind turbine platform including: a generatorconnected to a shaft having a shaft longitudinal axis; a set of turbineblades connected to the shaft and defining a blade plane that isperpendicular to the shaft longitudinal axis; a tower having a towerlongitudinal axis, the shaft being connected to the tower such thatthere is a non-zero angle between the blade plane and the towerlongitudinal axis; and at least three stabilizing columns, each of theat least three stabilizing columns having an internal volume forcontaining ballast, the first floating wind turbine platform having arated wind speed, a minimum wind speed, and a floating position in whichthe tower longitudinal axis is vertical, the ballast system comprising:at least one processor; and a machine-readable medium comprisinginstructions stored therein according to any of enumerated embodiments1-8.

11. A method for controlling an inclination of a first floating windturbine platform to reduce loads, the first floating wind turbineplatform including: a generator connected to a shaft having a shaftlongitudinal axis; a set of turbine blades connected to the shaft anddefining a blade plane that is perpendicular to the shaft longitudinalaxis; a tower having a tower longitudinal axis, the shaft beingconnected to the tower such that there is a non-zero angle between theblade plane and the tower longitudinal axis; at least three stabilizingcolumns, each of the at least three stabilizing columns having aninternal volume for containing ballast; and a ballast system fordistributing ballast, the first floating wind turbine platform having aminimum wind speed and a floating position in which the towerlongitudinal axis is vertical, the method comprising: receiving, by acontrol software module executing on a processor of the ballast system,inclination data associated with an inclination of the first floatingwind turbine platform; receiving, by the control software module, firstwind speed data and first wind direction data; determining, by thecontrol software module using the first wind speed data, a platform windspeed; determining, by the control software module using the first winddirection data, an angle of difference between the shaft longitudinalaxis and a wind direction, the angle of difference having a verticalcomponent relative to a horizontal plane; causing, by the controlsoftware module when the platform wind speed is below the minimum windspeed, the ballast system to distribute ballast to maintain the firstfloating wind turbine platform at the floating position; and causing, bythe control software module when the platform wind speed is greater thanthe minimum wind speed, the ballast system to distribute ballast toreduce the vertical component of the angle of difference to a firstvertical target angle chosen to minimize loads applied to the firstfloating wind turbine platform.

12. The method of claim 11 further comprising: receiving, by the controlsoftware module, the first vertical target angle from a second floatingwind turbine platform.

13. The method of claim 12 further comprising: receiving, by the controlsoftware module from the second floating wind turbine platform, secondwind speed data and second wind direction data; and comparing, by thecontrol software module, the second wind speed data to the first windspeed data and the second wind direction data to the first winddirection data, wherein the ballast system is caused to distributeballast to reduce the vertical component of the angle of difference tothe received first vertical target angle when both: the platform windspeed is greater than the minimum wind speed; and the comparisonindicates the first wind speed is within a first threshold from thesecond wind speed and the first wind direction is within a secondthreshold from the second wind direction.

14. The method of claim 12, wherein the first vertical target angle isreceived from the second wind turbine platform in response to the secondfloating wind turbine platform receiving the first wind speed data andthe first wind direction data.

15. The method of claim 11, wherein the first vertical target angle is achosen vertical target angle selected from among a plurality ofpotential vertical target angles in a numerical look-up table, thechosen vertical target angle selected based on at least one from thegroup: wind speed, wind direction, sea state, platform motion, andturbine motion.

16. The method of claim 11, wherein the first vertical target angle is acomputed vertical target angle computed as a function of at least onefrom the group: wind speed, wind direction, sea state, platform motion,and turbine motion.

17. The method of claim 11 further comprising: receiving, by the controlsoftware module executing on the processor, first power data regardingpower produced by the generator when the platform is inclined at thefirst vertical target angle, modifying, by the control software module,the first vertical target angle to a second vertical target angle;receiving, by the control software module, second power data regardingpower produced by the generator when the platform is inclined at thesecond vertical target angle; and maintaining, by the control softwaremodule, the inclination of the first floating wind turbine platform atthe second vertical target angle when the second power data is greaterthan the first power data.

18. The method of claim 11, wherein: the first wind speed data and firstwind direction data represent wind conditions at a location a distancefrom the first floating wind turbine platform; the determining theplatform wind speed uses the first wind speed data, the first winddirection data, the location, and the distance; the platform wind speedis an estimation of wind speed at the platform at a future time; and thevertical component relative to the horizontal plane is an estimate ofthe vertical component at the future time; the method furthercomprising: estimating, by the control software module based on thevertical component, a preparation amount of time required by the ballastsystem to reduce the vertical component to the first vertical targetangle, wherein: the causing, by the control software module when theplatform wind speed is greater than the minimum wind speed, the ballastsystem to distribute ballast to reduce the vertical component of theangle of difference to a first vertical target angle chosen to minimizeloads applied to the first floating wind turbine platform includes:causing, by the control software module when the platform wind speed isgreater than the minimum wind speed and less that the rated wind speed,the ballast system to begin to distribute ballast to reduce the verticalcomponent of the angle of difference to the first vertical target anglethe preparation amount of time in advance of the future time.

19. A non-transitory computer-readable medium comprising instructionsstored therein according to any of enumerated embodiments 11-18.

20. A ballast system for distributing ballast for controlling aninclination of a floating wind turbine platform to reduce loads, thefloating wind turbine platform including: a generator connected to ashaft having a shaft longitudinal axis; a set of turbine bladesconnected to the shaft and defining a blade plane that is perpendicularto the shaft longitudinal axis; a tower having a tower longitudinalaxis, the shaft being connected to the tower such that there is anon-zero angle between the blade plane and the tower longitudinal axis;and at least three stabilizing columns, each of the at least threestabilizing columns having an internal volume for containing ballast,the first floating wind turbine platform having a minimum wind speed anda floating position in which the tower longitudinal axis is vertical,the ballast system comprising: at least one processor; and amachine-readable medium comprising instructions stored therein accordingto any of enumerated embodiments 11-18.

21. A method for controlling an inclination of a floating wind turbineplatform to optimize power production, the floating wind turbineplatform including: a generator connected to a shaft having a shaftlongitudinal axis; a set of turbine blades connected to the shaft anddefining a blade plane that is perpendicular to the shaft longitudinalaxis; a tower having a tower longitudinal axis, the shaft beingconnected to the tower such that there is a non-zero angle between theblade plane and the tower longitudinal axis; at least three stabilizingcolumns, each of the at least three stabilizing columns having aninternal volume for containing ballast; and a ballast system fordistributing ballast, the floating wind turbine platform having a ratedwind speed, a minimum wind speed, and a floating position in which thetower longitudinal axis is vertical, the method comprising: receiving,by a control module executing on a processor, inclination dataassociated with an inclination of the floating wind turbine platform;receiving, by the control module, wind speed data and wind directiondata; determining, by the control module using the wind speed data, anacelle wind speed; determining, by the control module using the winddirection data, an angle of difference between the shaft longitudinalaxis and a wind direction, the angle of difference having a verticalcomponent relative to a horizontal plane; causing, by the control modulewhen the nacelle wind speed is below the minimum wind speed, the ballastsystem to distribute ballast to maintain the floating wind turbineplatform at the floating position; and causing, by the control modulewhen the nacelle wind speed is greater than the minimum wind speed andless that the rated wind speed, the ballast system to distribute ballastto reduce the vertical component of the angle of difference to avertical target angle chosen to optimize power produced by thegenerator.

22. The method of embodiment 21, wherein the angle of differenceincludes the vertical component and a horizontal component within thehorizontal plane, and the method further comprises: causing, by thecontrol module when the nacelle wind speed is greater than the minimumwind speed and less that the rated wind speed, the nacelle to rotatewith respect to the tower longitudinal axis to reduce the horizontalcomponent of the angle of difference to a horizontal target angle chosento optimize power produced by the generator.

23. The method of embodiment 21, wherein the vertical target angle iszero degrees.

24. The method of embodiment 21, wherein the vertical target angle is achosen vertical target angle selected from among a plurality ofpotential vertical target angles in a numerical look-up table, thechosen vertical target angle selected based on at least one from thegroup: wind speed, wind direction, sea state, platform motion, andturbine motion.

25. The method of embodiment 21, wherein the vertical target angle is acomputed vertical target angle computed as a function of at least onefrom the group: wind speed, wind direction, sea state, platform motion,and turbine motion.

26. The method of embodiment 21, wherein the vertical target angle istransmitted by another platform in the wind farm which experienced or isexperiencing the same conditions and already performed the optimization.

27. The method of embodiment 21 further comprising: receiving, by thecontrol module executing on the processor, power data regarding powerproduced by the generator, wherein the vertical target angle is chosenbased in part on the power data.

28. The method of embodiment 21, wherein: the wind speed data and winddirection data represent wind conditions at a location a distance fromthe floating wind turbine platform; the determining the nacelle windspeed uses the wind speed data, the direction data, the location, andthe distance; the nacelle wind speed is an estimation of wind speed atthe nacelle at a future time; and the vertical component relative to thehorizontal plane is an estimate of the vertical component at the futuretime; the method further comprising: estimating, by the control modulebased on the vertical component, a preparation amount of time requiredby the ballast system to reduce the vertical component to the verticaltarget angle, wherein: the causing, by the control module when thenacelle wind speed is greater than the minimum wind speed and less thatthe rated wind speed, the ballast system to distribute ballast to reducethe vertical component of the angle of difference to a vertical targetangle chosen to optimize power produced by the generator includes:causing, by the control module when the nacelle wind speed is greaterthan the minimum wind speed and less that the rated wind speed, theballast system to begin to distribute ballast to reduce the verticalcomponent of the angle of difference to the vertical target angle thepreparation amount of time in advance of the future time.

29. The method of embodiment 21, wherein the floating wind turbineplatform is level in the floating position.

30. The method of embodiment 21, wherein the distributing ballast toreduce the angle of difference between the blade plane and verticalcauses the floating wind turbine platform to incline into the wind, orcauses the floating wind turbine platform to incline away from the wind.

31. A non-transitory computer-readable medium comprising instructionsstored therein according to any of enumerated embodiments 21-30.

32. A system for controlling an inclination of a floating wind turbineplatform to optimize power production, the floating wind turbineplatform including: a generator connected to a shaft having a shaftlongitudinal axis; a set of turbine blades connected to the shaft anddefining a blade plane that is perpendicular to the shaft longitudinalaxis; a tower having a tower longitudinal axis, the shaft beingconnected to the tower such that there is a non-zero angle between theblade plane and the tower longitudinal axis; at least three stabilizingcolumns, each of the at least three stabilizing columns having aninternal volume for containing ballast; and a ballast system fordistributing ballast, the floating wind turbine platform having a ratedwind speed, a minimum wind speed, and a floating position in which thetower longitudinal axis is vertical, the system comprising: one or moreprocessors; and a machine-readable medium comprising instructions storedtherein according to any of enumerated embodiments 21-30.

33. A method for controlling an inclination of a floating wind turbineplatform to reduce static loads at the base of tower and on the floatingstructure, the floating wind turbine platform including: a generatorconnected to a shaft having a shaft longitudinal axis; a set of turbineblades connected to the shaft and defining a blade plane that isperpendicular to the shaft longitudinal axis; a tower having a towerlongitudinal axis, the shaft being connected to the tower such thatthere is a non-zero angle between the blade plane and the towerlongitudinal axis; at least three stabilizing columns, each of the atleast three stabilizing columns having an internal volume for containingballast; and a ballast system for distributing ballast, the floatingwind turbine platform having a minimum wind speed and a floatingposition in which the tower longitudinal axis is vertical, the methodcomprising: receiving, by a control module executing on a processor,inclination data associated with an inclination of the floating windturbine platform; receiving, by the control module, wind speed data andwind direction data; determining, by the control module using the windspeed data, a nacelle wind speed; determining, by the control moduleusing the wind direction data, an angle of difference between the shaftlongitudinal axis and a wind direction, the angle of difference having avertical component relative to a horizontal plane; causing, by thecontrol module when the nacelle wind speed is below the minimum windspeed, the ballast system to distribute ballast to maintain the floatingwind turbine platform at the floating position; and causing, by thecontrol module when the nacelle wind speed is greater than the minimumwind speed, the ballast system to distribute ballast to reduce thevertical component of the angle of difference to a vertical target anglechosen to minimize loads applied to the floating wind turbine platform.

34. The method of embodiment 33, wherein the angle of differenceincludes the vertical component and a horizontal component within thehorizontal plane, and the method further comprises; causing, by thecontrol module when the nacelle wind speed is greater than the minimumwind speed and less that the rated wind speed, the nacelle to rotatewith respect to the tower longitudinal axis to reduce the horizontalcomponent of the angle of difference to a horizontal target angle chosento minimize loads applied to the floating wind turbine platform.

35. The method of embodiment 33, wherein the vertical target angle iszero degrees.

36. The method of embodiment 33, wherein the vertical target angle is achosen vertical target angle selected from among a plurality ofpotential vertical target angles in a numerical look-up table, thechosen vertical target angle selected based on at least one from thegroup: wind speed, wind direction, sea state, platform motion, andturbine motion.

37. The method of embodiment 33, wherein the vertical target angle is acomputed vertical target angle computed as a function of at least onefrom the group: wind speed, wind direction, sea state, platform motion,and turbine motion.

38. The method of embodiment 33, wherein the vertical target angle istransmitted by another platform in the wind farm which experienced or isexperiencing the same conditions and already performed the optimization.

39. The method of embodiment 33 further comprising: receiving, by thecontrol module executing on the processor, power data regarding powerproduced by the generator, wherein the vertical target angle is chosenbased in part on the power data or the stress data measured on thestructure.

40. The method of embodiment 33 further comprising: receiving, by thecontrol module executing on the processor, stress data regarding thestress at critical locations at the base of tower and on the floatingplatform, wherein the vertical target angle is chosen based in part onthe stress data.

41. The method of embodiment 33, wherein: the wind speed data and winddirection data represent wind conditions at a location a distance fromthe floating wind turbine platform; the determining the nacelle windspeed uses the wind speed data, the direction data, the location, andthe distance; the nacelle wind speed is an estimation of wind speed atthe nacelle at a future time; and the vertical component relative to thehorizontal plane is an estimate of the vertical component at the futuretime; the method further comprising: estimating, by the control modulebased on the vertical component, a preparation amount of time requiredby the ballast system to reduce the vertical component to the verticaltarget angle, wherein: the instructions causing, by the control modulewhen the nacelle wind speed is greater than the minimum wind speed, theballast system to distribute ballast to reduce the vertical component ofthe angle of difference to a vertical target angle chosen to minimizeloads applied to the floating wind turbine platform include: causing, bythe control module when the nacelle wind speed is greater than theminimum wind speed and less that the rated wind speed, the ballastsystem to begin to distribute ballast to reduce the vertical componentof the angle of difference to the vertical target angle the preparationamount of time in advance of the future time.

42. A non-transitory computer-readable medium comprising instructionsstored therein according to any of enumerated embodiments 33-41.

43. A system for controlling an inclination of a floating wind turbineplatform to reduce loads, the floating wind turbine platform including:a generator connected to a shaft having a shaft longitudinal axis; a setof turbine blades connected to the shaft and defining a blade plane thatis perpendicular to the shaft longitudinal axis; a tower having a towerlongitudinal axis, the shaft being connected to the tower such thatthere is a non-zero angle between the blade plane and the towerlongitudinal axis; at least three stabilizing columns, each of the atleast three stabilizing columns having an internal volume for containingballast; and a ballast system for distributing ballast, the floatingwind turbine platform having a minimum wind speed and a floatingposition in which the tower longitudinal axis is vertical, the systemcomprising: one or more processors; and a machine-readable mediumcomprising instructions stored therein according to any of enumeratedembodiments 33-41.

It is understood that any specific order or hierarchy of steps in anydisclosed process is an illustration of an approach. Based upon designpreferences, it is understood that the specific order or hierarchy ofsteps in the processes may be rearranged, or that not all illustratedsteps be performed. Some of the steps may be performed simultaneously.

Moreover, the separation of various apparatus components in theembodiments described above should not be understood as requiring suchseparation in all embodiments.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the embodiments are not intended to be limited tothe aspects shown herein, but are to be accorded the full scopeconsistent with the language embodiments, wherein reference to anelement in the singular is not intended to mean “one and only one”unless specifically so stated, but rather “one or more.” Unlessspecifically stated otherwise, the term “some” refers to one or more.Pronouns in the masculine (e.g., his) include the feminine and neutergender (e.g., her and its) and vice versa. Headings and subheadings, ifany, are used for convenience only and do not limit the subjectdisclosure.

A phrase such as an “aspect” does not imply that such aspect isessential to the subject technology or that such aspect applies to allconfigurations of the subject technology. A disclosure relating to anaspect may apply to all configurations, or one or more configurations. Aphrase such as an aspect may refer to one or more aspects and viceversa. A phrase such as a “configuration” does not imply that suchconfiguration is essential to the subject technology or that suchconfiguration applies to all configurations of the subject technology. Adisclosure relating to a configuration may apply to all configurations,or one or more configurations. A phrase such as a configuration mayrefer to one or more configurations and vice versa.

All structural and functional equivalents to the elements of the variousaspects described throughout this disclosure that are known or latercome to be known to those of ordinary skill in the art are expresslyincorporated herein by reference and are intended to be encompassed bythe claims.

We claim:
 1. A non-transitory computer-readable medium comprisinginstructions stored therein for controlling an inclination of a firstfloating wind turbine platform to optimize power production, the firstfloating wind turbine platform including: a generator connected to ashaft having a shaft longitudinal axis; a set of turbine bladesconnected to the shaft and defining a blade plane that is perpendicularto the shaft longitudinal axis; a tower having a tower longitudinalaxis, the shaft being connected to the tower such that there is anon-zero angle between the blade plane and the tower longitudinal axis;at least three stabilizing columns, each of the at least threestabilizing columns having an internal volume for containing ballast;and a ballast system for distributing ballast, the first floating windturbine platform having a rated wind speed, a minimum wind speed, and afloating position in which the tower longitudinal axis is vertical, andthe instructions, which when executed by at least one processor of theballast system, cause the at least one processor to perform operationscomprising: receiving inclination data associated with an inclination ofthe first floating wind turbine platform; receiving first wind speeddata and first wind direction data; determining, using the first windspeed data, a platform wind speed; determining, using the first winddirection data, an angle of difference between the shaft longitudinalaxis and a wind direction, the angle of difference having a verticalcomponent relative to a horizontal plane; causing, when the platformwind speed is below the minimum wind speed, the ballast system todistribute ballast to maintain the first floating wind turbine platformat the floating position; and causing, when the platform wind speed isgreater than the minimum wind speed and less that the rated wind speed,the ballast system to distribute ballast to lean the first floating windturbine platform a first angle of inclination chosen to reduce thevertical component of the angle of difference to a first vertical targetangle to optimize power production.
 2. The computer-readable medium ofclaim 1, the instructions further causing the at least one processor toperform operations comprising: receiving the first angle of inclinationfrom a second floating wind turbine platform.
 3. The computer-readablemedium of claim 2, the instructions further causing the at least oneprocessor to perform operations comprising: receiving, from the secondfloating wind turbine platform, second wind speed data and second winddirection data; and comparing the second wind speed data to the firstwind speed data and the second wind direction data to the first winddirection data, wherein the ballast system is caused to distributeballast to lean the first floating wind turbine platform the first angleof inclination when both: the platform wind speed is greater than theminimum wind speed and less that the rated wind speed; and thecomparison indicates the first wind speed is within a first thresholdfrom the second wind speed and the first wind direction is within asecond threshold from the second wind direction.
 4. Thecomputer-readable medium of claim 2, wherein the first angle ofinclination is received from the second wind turbine platform inresponse to the second floating wind turbine platform receiving thefirst wind speed data and the first wind direction data.
 5. Thecomputer-readable medium of claim 1, wherein the first vertical targetangle is a chosen vertical target angle selected from among a pluralityof potential vertical target angles in a numerical look-up table, thechosen vertical target angle selected based on at least one from thegroup: first wind speed, first wind direction, sea state, platformmotion, and turbine motion.
 6. The computer-readable medium of claim 1,wherein the first vertical target angle is a computed vertical targetangle computed as a function of at least one from the group: first windspeed, first wind direction, sea state, platform motion, and turbinemotion.
 7. The computer-readable medium of claim 1, the instructionsfurther causing the at least one processor to perform operationscomprising: receiving first power data regarding power produced by thegenerator when the platform has attained the first vertical targetangle; modifying the first vertical target angle to a second verticaltarget angle; receiving second power data regarding power produced bythe generator when the platform has attained the second vertical targetangle; and maintaining the first floating wind turbine platform at asecond angle of inclination associated with the second vertical targetangle when the second power data is greater than the first power data.8. The computer-readable medium of claim 1, wherein: the first windspeed data and first wind direction data represent wind conditions at alocation a distance from the first floating wind turbine platform; thedetermining the platform wind speed uses the first wind speed data, thefirst wind direction data, the location, and the distance; the platformwind speed is an estimation of wind speed at the platform at a futuretime; and the vertical component relative to the horizontal plane is anestimate of the vertical component at the future time; the instructionsfurther causing the at least one processor to perform operationscomprising: estimating, based on the first angle of inclination, apreparation amount of time required by the ballast system to lean thefirst floating wind turbine platform the first angle of inclination,wherein: the causing, when the platform wind speed is greater than theminimum wind speed and less that the rated wind speed, the ballastsystem to distribute ballast to lean the first floating wind turbineplatform a first angle of inclination chosen to reduce the verticalcomponent of the angle of difference to a first vertical target anglechosen to optimize power production includes: causing, when the platformwind speed is greater than the minimum wind speed and less that therated wind speed, the ballast system to begin to distribute ballast tolean the first floating wind turbine platform a first angle ofinclination chosen to reduce the vertical component of the angle ofdifference to the first vertical target angle the preparation amount oftime in advance of the future time.
 9. The computer-readable medium ofclaim 1, wherein: the first floating wind turbine platform is one of aplurality of floating wind turbine platforms of a windfarm; the firstangle of inclination is chosen to optimize the power production of thewindfarm; and the causing the ballast system to distribute ballast tolean the first floating wind turbine platform a first angle ofinclination results in the first floating wind turbine platformproducing sub-optimal power.
 10. A ballast system for distributingballast for controlling an inclination of a first floating wind turbineplatform to optimize power production, the first floating wind turbineplatform including: a generator connected to a shaft having a shaftlongitudinal axis; a set of turbine blades connected to the shaft anddefining a blade plane that is perpendicular to the shaft longitudinalaxis; a tower having a tower longitudinal axis, the shaft beingconnected to the tower such that there is a non-zero angle between theblade plane and the tower longitudinal axis; and at least threestabilizing columns, each of the at least three stabilizing columnshaving an internal volume for containing ballast, the first floatingwind turbine platform having a rated wind speed, a minimum wind speed,and a floating position in which the tower longitudinal axis isvertical, the ballast system comprising: at least one processor; and amachine-readable medium comprising instructions stored therein, whichwhen executed by the at least one processor, cause the at least oneprocessor to perform operations comprising: receiving inclination dataassociated with an inclination of the first floating wind turbineplatform; receiving first wind speed data and first wind direction data;determining, using the first wind speed data, a platform wind speed;determining, using the first wind direction data, an angle of differencebetween the shaft longitudinal axis and a wind direction, the angle ofdifference having a vertical component relative to a horizontal plane;causing, when the platform wind speed is below the minimum wind speed,the ballast system to distribute ballast to maintain the first floatingwind turbine platform at the floating position; and causing, when theplatform wind speed is greater than the minimum wind speed and less thatthe rated wind speed, the ballast system to distribute ballast to leanthe first floating wind turbine platform a first angle of inclinationchosen to reduce the vertical component of the angle of difference to afirst vertical target angle to optimize power production.
 11. The systemof claim 10, the instructions further causing the at least one processorto perform operations comprising: receiving the first angle ofinclination from a second floating wind turbine platform.
 12. The systemof claim 11, the instructions further causing the at least one processorto perform operations comprising: receiving, from the second floatingwind turbine platform, second wind speed data and second wind directiondata; and comparing the second wind speed data to the first wind speeddata and the second wind direction data to the first wind directiondata, wherein the ballast system is caused to distribute ballast to leanthe first floating wind turbine platform the first angle of inclinationwhen both: the platform wind speed is greater than the minimum windspeed and less that the rated wind speed; and the comparison indicatesthe first wind speed is within a first threshold from the second windspeed and the first wind direction is within a second threshold from thesecond wind direction.
 13. The system of claim 11, wherein the firstangle of inclination is received from the second wind turbine platformin response to the second floating wind turbine platform receiving thefirst wind speed data and the first wind direction data.
 14. The systemof claim 10, wherein the first vertical target angle is a chosenvertical target angle selected from among a plurality of potentialvertical target angles in a numerical look-up table, the chosen verticaltarget angle selected based on at least one from the group: first windspeed, first wind direction, sea state, platform motion, and turbinemotion.
 15. The system of claim 10, wherein the first vertical targetangle is a computed vertical target angle computed as a function of atleast one from the group: first wind speed, first wind direction, seastate, platform motion, and turbine motion.
 16. The system of claim 10,the instructions further causing the at least one processor to performoperations comprising: receiving first power data regarding powerproduced by the generator when the platform has attained the firstvertical target angle; modifying the first vertical target angle to asecond vertical target angle; receiving second power data regardingpower produced by the generator when the platform has attained thesecond vertical target angle; and maintaining the first floating windturbine platform at a second angle of inclination associated with thesecond vertical target angle when the second power data is greater thanthe first power data.
 17. The system of claim 10, wherein: the firstwind speed data and first wind direction data represent wind conditionsat a location a distance from the first floating wind turbine platform;the determining the platform wind speed uses the first wind speed data,the first wind direction data, the location, and the distance; theplatform wind speed is an estimation of wind speed at the platform at afuture time; and the vertical component relative to the horizontal planeis an estimate of the vertical component at the future time; theinstructions further causing the at least one processor to performoperations comprising: estimating, based on the first angle ofinclination, a preparation amount of time required by the ballast systemto lean the first floating wind turbine platform the first angle ofinclination, wherein: the causing, when the platform wind speed isgreater than the minimum wind speed and less that the rated wind speed,the ballast system to distribute ballast to lean the first floating windturbine platform a first angle of inclination chosen to reduce thevertical component of the angle of difference to a first vertical targetangle chosen to optimize power production includes: causing, when theplatform wind speed is greater than the minimum wind speed and less thatthe rated wind speed, the ballast system to begin to distribute ballastto lean the first floating wind turbine platform a first angle ofinclination chosen to reduce the vertical component of the angle ofdifference to the first vertical target angle the preparation amount oftime in advance of the future time.
 18. The system of claim 10, wherein:the first floating wind turbine platform is one of a plurality offloating wind turbine platforms of a windfarm; the first angle ofinclination is chosen to optimize the power production of the windfarm;and the causing the ballast system to distribute ballast to lean thefirst floating wind turbine platform a first angle of inclinationresults in the first floating wind turbine platform producingsub-optimal power.
 19. A non-transitory computer-readable mediumcomprising instructions stored therein for controlling an inclination ofa first floating wind turbine platform to reduce loads, the firstfloating wind turbine platform including: a generator connected to ashaft having a shaft longitudinal axis; a set of turbine bladesconnected to the shaft and defining a blade plane that is perpendicularto the shaft longitudinal axis; a tower having a tower longitudinalaxis, the shaft being connected to the tower such that there is anon-zero angle between the blade plane and the tower longitudinal axis;at least three stabilizing columns, each of the at least threestabilizing columns having an internal volume for containing ballast;and a ballast system for distributing ballast, the first floating windturbine platform having a rated wind speed, a minimum wind speed, and afloating position in which the tower longitudinal axis is vertical, andthe instructions, which when executed by at least one processor of theballast system, cause the at least one processor to perform operationscomprising: receiving inclination data associated with an inclination ofthe first floating wind turbine platform; receiving first wind speeddata and first wind direction data; determining, using the first windspeed data, a platform wind speed; determining, using the first winddirection data, an angle of difference between the shaft longitudinalaxis and a wind direction, the angle of difference having a verticalcomponent relative to a horizontal plane; causing, when the platformwind speed is below the minimum wind speed, the ballast system todistribute ballast to maintain the first floating wind turbine platformat the floating position; and causing, when the platform wind speed isgreater than the minimum wind speed and less that the rated wind speed,the ballast system to distribute ballast to lean the first floating windturbine platform a first angle of inclination chosen to reduce thevertical component of the angle of difference to a first vertical targetangle to minimize loads applied to the first floating wind turbineplatform.
 20. The computer-readable medium of claim 19, the instructionsfurther causing the at least one processor to perform operationscomprising: receiving the first angle of inclination from a secondfloating wind turbine platform.
 21. The computer-readable medium ofclaim 20, the instructions further causing the at least one processor toperform operations comprising: receiving, from the second floating windturbine platform, second wind speed data and second wind direction data;and comparing, the second wind speed data to the first wind speed dataand the second wind direction data to the first wind direction data,wherein the ballast system is caused to distribute ballast to lean thefirst floating wind turbine platform the first angle of inclination whenboth: the platform wind speed is greater than the minimum wind speed;and the comparison indicates the first wind speed is within a firstthreshold from the second wind speed and the first wind direction iswithin a second threshold from the second wind direction.
 22. Thecomputer-readable medium of claim 20, wherein the first angle ofinclination is received from the second wind turbine platform inresponse to the second floating wind turbine platform receiving thefirst wind speed data and the first wind direction data.
 23. Thecomputer-readable medium of claim 19, wherein the first vertical targetangle is a chosen vertical target angle selected from among a pluralityof potential vertical target angles in a numerical look-up table, thechosen vertical target angle selected based on at least one from thegroup: wind speed, wind direction, sea state, platform motion, andturbine motion.
 24. The computer-readable medium of claim 19, whereinthe first vertical target angle is a computed vertical target anglecomputed as a function of at least one from the group: wind speed, winddirection, sea state, platform motion, and turbine motion.
 25. Thecomputer-readable medium of claim 19, the instructions further causingthe at least one processor to perform operations comprising: receivingfirst power data regarding power produced by the generator when theplatform has attained the first vertical target angle; modifying thefirst vertical target angle to a second vertical target angle; receivingsecond power data regarding power produced by the generator when theplatform has attained the second vertical target angle; and maintainingthe first floating wind turbine platform at a second angle ofinclination associated with the second vertical target angle when thesecond power data is greater than the first power data.
 26. Thecomputer-readable medium of claim 19, wherein: the first wind speed dataand first wind direction data represent wind conditions at a location adistance from the first floating wind turbine platform; the determiningthe platform wind speed uses the first wind speed data, the first winddirection data, the location, and the distance; the platform wind speedis an estimation of wind speed at the platform at a future time; and thevertical component relative to the horizontal plane is an estimate ofthe vertical component at the future time; the instructions furthercausing the at least one processor to perform operations comprising:estimating, based on the first angle of inclination, a preparationamount of time required by the ballast system to lean the first floatingwind turbine platform the first angle of inclination, wherein: thecausing, when the platform wind speed is greater than the minimum windspeed, the ballast system to distribute ballast to lean the firstfloating wind turbine platform a first angle of inclination chosen toreduce the vertical component of the angle of difference to a firstvertical target angle chosen to minimize loads applied to the firstfloating wind turbine platform includes: causing, when the platform windspeed is greater than the minimum wind speed and less that the ratedwind speed, the ballast system to begin to distribute ballast to leanthe first floating wind turbine platform a first angle of inclinationchosen to reduce the vertical component of the angle of difference tothe first vertical target angle the preparation amount of time inadvance of the future time.
 27. A ballast system for distributingballast for controlling an inclination of a first floating wind turbineplatform to reduce loads, the first floating wind turbine platformincluding: a generator connected to a shaft having a shaft longitudinalaxis; a set of turbine blades connected to the shaft and defining ablade plane that is perpendicular to the shaft longitudinal axis; atower having a tower longitudinal axis, the shaft being connected to thetower such that there is a non-zero angle between the blade plane andthe tower longitudinal axis; and at least three stabilizing columns,each of the at least three stabilizing columns having an internal volumefor containing ballast, the first floating wind turbine platform havinga rated wind speed, a minimum wind speed, and a floating position inwhich the tower longitudinal axis is vertical, the ballast systemcomprising: at least one processor; and a machine-readable mediumcomprising instructions stored therein, which when executed by the atleast one processor, cause the at least one processor to performoperations comprising: receiving inclination data associated with aninclination of the first floating wind turbine platform; receiving firstwind speed data and first wind direction data; determining, using thefirst wind speed data, a platform wind speed; determining, using thefirst wind direction data, an angle of difference between the shaftlongitudinal axis and a wind direction, the angle of difference having avertical component relative to a horizontal plane; causing, when theplatform wind speed is below the minimum wind speed, the ballast systemto distribute ballast to maintain the first floating wind turbineplatform at the floating position; and causing, when the platform windspeed is greater than the minimum wind speed and less that the ratedwind speed, the ballast system to distribute ballast to lean the firstfloating wind turbine platform a first angle of inclination chosen toreduce the vertical component of the angle of difference to a firstvertical target angle to minimize loads applied to the first floatingwind turbine platform.
 28. The system of claim 27, the instructionsfurther causing the at least one processor to perform operationscomprising: receiving the first angle of inclination from a secondfloating wind turbine platform.
 29. The system of claim 28, theinstructions further causing the at least one processor to performoperations comprising: receiving, from the second floating wind turbineplatform, second wind speed data and second wind direction data; andcomparing the second wind speed data to the first wind speed data andthe second wind direction data to the first wind direction data, whereinthe ballast system is caused to distribute ballast to lean the firstfloating wind turbine platform the first angle of inclination when both:the platform wind speed is greater than the minimum wind speed; and thecomparison indicates the first wind speed is within a first thresholdfrom the second wind speed and the first wind direction is within asecond threshold from the second wind direction.
 30. The system of claim28, wherein the first angle of inclination is received from the secondwind turbine platform in response to the second floating wind turbineplatform receiving the first wind speed data and the first winddirection data.
 31. The system of claim 27, wherein the first verticaltarget angle is a chosen vertical target angle selected from among aplurality of potential vertical target angles in a numerical look-uptable, the chosen vertical target angle selected based on at least onefrom the group: wind speed, wind direction, sea state, platform motion,and turbine motion.
 32. The system of claim 27, wherein the firstvertical target angle is a computed vertical target angle computed as afunction of at least one from the group: wind speed, wind direction, seastate, platform motion, and turbine motion.
 33. The system of claim 27,the instructions further causing the at least one processor to performoperations comprising: receiving first power data regarding powerproduced by the generator when the platform has attained the firstvertical target angle; modifying the first vertical target angle to asecond vertical target angle; receiving second power data regardingpower produced by the generator when the platform has attained thesecond vertical target angle; and maintaining the first floating windturbine platform at a second angle of inclination associated with thesecond vertical target angle when the second power data is greater thanthe first power data.
 34. The system of claim 27, wherein: the firstwind speed data and first wind direction data represent wind conditionsat a location a distance from the first floating wind turbine platform;the determining the platform wind speed uses the first wind speed data,the first wind direction data, the location, and the distance; theplatform wind speed is an estimation of wind speed at the platform at afuture time; and the vertical component relative to the horizontal planeis an estimate of the vertical component at the future time; theinstructions further causing the at least one processor to performoperations comprising: estimating, based on the first angle ofinclination, a preparation amount of time required by the ballast systemto lean the first floating wind turbine platform the first angle ofinclination, wherein: the causing, when the platform wind speed isgreater than the minimum wind speed, the ballast system to distributeballast to lean the first floating wind turbine platform a first angleof inclination chosen to reduce the vertical component of the angle ofdifference to a first vertical target angle chosen to minimize loadsapplied to the first floating wind turbine platform includes: causing,when the platform wind speed is greater than the minimum wind speed andless that the rated wind speed, the ballast system to begin todistribute ballast to lean the first floating wind turbine platform afirst angle of inclination chosen to reduce the vertical component ofthe angle of difference to the first vertical target angle thepreparation amount of time in advance of the future time.